Editor’s Note: This Fortune classic, from our January 2008 issue, is the first solo profile that Melinda Gates ever agreed to do. The story covers the marvelous gamut of Melinda’s extraordinary life: meeting and marrying Bill Gates, becoming the essential half of what has turned out to be the world’s premier philanthropic partnership, and dramatically changing her husband’s ideas about what to do with his money. Another rich guy, Warren Buffett, tells Fortune that he sees himself and his late wife, Susie, in Bill and Melinda—and that is just one reason why Buffett calls the Gateses “the perfect solution” to manage and disperse his billions to philanthropy.

Years before Melinda French met and married Bill Gates, she had a love affair—with an Apple computer.

She was growing up in Dallas in a hard-working middle-class family. Ray French, Melinda‘s dad, stretched their budget to pay for all four children to go to college. An engineer, he started a family business on the side, operating rental properties. “That meant scrubbing floors and cleaning ovens and mowing the lawns,” Melinda recalls. The whole family pitched in every weekend. When Ray brought home an Apple III computer one day when she was 16, she was captivated. “We would help him run the business and keep the books,” she says. “We saw money coming in and money going out.”

Of all the tricks that life can play, it’s hard to imagine any stranger than what befell Melinda French. Today she is living in a gargantuan high-tech mansion on the shores of Lake Washington, married to the richest man in America—and giving billions of dollars away. When she married Bill Gates 14 years ago, she bought into a complex bargain. On the one hand, she became half of what has turned out to be the world’s premier philanthropic partnership. The Bill & Melinda Gates Foundation has assets of $37.6 billion, making it the world’s largest. In that total is $3.4 billion that Warren Buffett has already given, and still to come are nine million Berkshire Hathaway B shares, currently worth $41 billion, that he has pledged to contribute in coming years. Assuming that Berkshire shares continue to rise and that the Gateses continue to bestow their own wealth on their foundation, Melinda and Bill will very likely give away more than $100 billion in their lifetimes. Already the foundation has disbursed $14.4 billion—more than the Rockefeller Foundation has distributed since its creation in 1913 (even adjusted for inflation).

Along the way, Melinda has sacrificed privacy, security, simplicity, and normalcy. In the late 1990s, during the Microsoft msft antitrust trial, her husband was widely regarded as the biggest bully in business. And isn’t anyone married to Bill Gates susceptible to losing her identity—to being perceived as the ultimate accessory?

Forgive her if she overcompensates. One day this past fall she spent many hours at her children’s school (the Gateses have two daughters, ages 5 and 11, and a son, 8) and then hosted a dozen dinner guests, including four African health ministers who were in Seattle for the Bill & Melinda Gates Foundation Malaria Forum. By 10 P.M., after everyone had left, she was feeling frazzled and panicky about her speech the next morning. “Just go to bed!” Bill told her. “You know so much about malaria.” Melinda dreads the spotlight, but the following morning she faced more than 300 scientists, doctors, and health officials. She unveiled an audacious plan to eradicate malaria—a disease that kills more than one million people annually and has eluded a cure for centuries—and then answered questions with Bill. Afterward the crowd buzzed about this woman whom even they, recipients of the Gateses‘ billions, hardly know.

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Today, at 43, Melinda Gates is ready to reveal her full self—to go public, so to speak. “I had always thought that when my youngest child started full-day school I’d step up,” she says, sitting down with Fortune for her first-ever profile. Although she admits she would prefer to stay out of public view forever, her older daughter got her thinking. “I really want her to have a voice, whatever she chooses to do,” she says. “I need to role-model that for her.” She is spending more time on foundation work, up to 30 hours a week. “As I thought about strong women of history, I realized that they stepped out in some way.”

She is stepping up also because her husband is doing the same. Beginning in July, Bill, who is nine years older than Melinda, plans to spend more than 40 hours a week on philanthropy, leaving 15 or so for his duties as chairman of Microsoft. Friends of the couple say that he wouldn’t be shifting gears if it weren’t for Melinda. Moreover, they say, she has helped Bill become more open, patient, and compassionate. “Bullshit!” he bellows. Nicer, perhaps? “No way!” he shouts, grinning because he knows it’s true. One thing he admits readily: Thanks to Melinda, he is easing comfortably into his new role. About the philanthropic work he says, “I don’t think it would be fun to do on my own, and I don’t think I’d do as much of it.”

This is not exactly a marriage of equals. Melinda is better educated than Bill, having graduated from Duke University with a BA (a double major in computer science and economics) and an MBA. Harvard’s most celebrated dropout, Bill was awarded an honorary degree last June. Melinda also outperforms him athletically. She runs once a week with a few friends—seven miles in an hour, a brisk pace—and tries to exercise five days a week. She has completed the Seattle marathon and climbed, with ropes and crampons, to the peak of 14,410-foot Mount Rainier. As for Bill, Melinda says, “He’s finally started to run in the last year.” To give him credit, he is an aggressive tennis player and a decent golfer—sometimes playing with Melinda. Beyond that, though, running on the treadmill while watching DVDs three nights a week is all Bill can do to keep up with his fit wife.

Melinda also understands people better than he does, Bill admits. In fact, he uses her as a sounding board, sometimes for personnel matters at Microsoft. In 2000, when Steve Ballmer, with whom Bill has worked for 28 years, replaced him as CEO, Melinda helped ease the awkward transition. “Melinda and I would brainstorm about it,” Bill says. “You always benefit from your key confidante telling you, ‘You think so-and-so stepped on your toes? Well, maybe he didn’t mean to. Maybe you’re wrong.'” Says the couple’s close friend Warren Buffett, who has known them since 1991: “Bill really needs her.”

When it comes to investing their philanthropic assets, Melinda wields even greater influence. Early on she and Bill agreed to focus on a few areas of giving, choosing where to place their money by asking two questions: Which problems affect the most people? And which have been neglected in the past? While many philanthropists take the same tack, the Gateses, who love puzzles, apply particular rigor. “We literally go down the chart of the greatest inequities and give where we can effect the greatest change,” Melinda says. So while they don’t give to the American Cancer Society, they have pumped billions into the world’s deadliest diseases—most importantly AIDS, malaria, and tuberculosis—and failing public high schools in the U.S. And while Bill is drawn, naturally, to vaccine research and scientific solutions that may be decades away, Melinda is interested in alleviating suffering right now. “You can’t save kids just with vaccines,” she says. “I’d go into rural villages in India and think, ‘Okay, we saved this child. But the cows are defecating in the stream coming into the village. There are other things we need to be doing.'”

Those other things include funding insecticide-treated bed nets to ward off malaria-carrying mosquitoes, providing microbicides to prevent the transmission of AIDS, and offering microloans and insurance to help the poorest of the poor start businesses and farms. The Gateses‘ latest mission, which developed out of a trip Melinda took to Kenya two years ago, is to recreate for Africa a green revolution similar to the program that increased crop yields in Latin America and Asia beginning in the 1940s. In 2006 the Gates Foundation formed a $150 million alliance with the Rockefeller Foundation. “Melinda is a total-systems thinker,” says Rockefeller president Judith Rodin. “She and Bill dive into issues. They care deeply, deeply, deeply about making a difference, but they don’t get starry-eyed. They demand impact.”

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The impact comes from the combination of Melinda‘s holistic vision and Bill’s brainpower. Bono, the rock star-humanitarian who is both a friend of the Gateses and a grantee (through his One antipoverty campaign), calls their relationship “symbiotic.” Noting Bill’s fierceness, Bono says, “Sometimes I call him Kill Bill. Lots of people like him—and I include myself—are enraged, and we sweep ourselves into a fury at the wanton loss of lives. What we need is a much slower pulse to help us be rational. Melinda is that pulse.” Buffett also believes that Melinda makes Bill a better decision-maker. “He’s smart as hell, obviously,” Buffett says. “But in terms of seeing the whole picture, she’s smarter.” Would Buffett have given the Gates Foundation his fortune if Melindawere not in the picture? “That’s a great question,” he replies. “And the answer is, I’m not sure.”

A Goal a Day

If you are successful, it is because somewhere, sometime, someone gave you a life or an idea that started you in the right direction. Remember also that you are indebted to life until you help some less fortunate person, just as you were helped. —Melinda Gates, Valedictory speech, Ursuline Academy, 1982

Unlike William H. Gates III, whose parents, Bill and Mary, were civic leaders in Seattle, Melinda French grew up not knowing privilege or wealth. Her father worked on the space program at LTV. Her mother was a stay-at-home mom who didn’t go to college and regretted it. Says Melinda, who has one sister 14 months older and two younger brothers: “My parents told us, ‘No matter what college you get into, we will pay for it.'”

That Apple III was actually the family’s second computer; when Melinda was 14, her father brought home an Apple II, the first consumer computer on the market. “I finagled it to be in my bedroom so I could play games on it,” she says. She learned BASIC, the programming language, and taught it to other kids during summer vacations.

Life was a test, and Melinda believed she had to ace it. Susan Bauer, her math and computer science teacher at Ursuline Academy, an all-girls Catholic high school in Dallas, recalls, “Every day she had a goal.” Melinda laughs, a bit embarrassed at the mention: “The goals were run a mile, learn a new word, that sort of thing.” During her freshman year she looked up recent graduates’ college choices. She discovered that only Ursuline’s top two students had gotten into elite schools. “I realized that the only way to get into a good college was to be valedictorian or salutatorian. So that was my goal,” she explains. She hoped to go to Notre Dame.

Didn’t we all know this girl in high school? The star student, captain of the drill team, candy striper in the hospital, tutor at the public school on the other side of the tracks? Melinda was all that. At Ursuline, where the motto is Serviam (Latin for “I will serve”), volunteerism was a requirement. Her ambition, insists Bauer, “was never abrasive. Never. She was always lovely and charming, and she would win people over by being persuasive.”

She made valedictorian and got into Notre Dame. But Notre Dame did not get her. When she and her dad visited, she recalls, officials at the university told them that “computers are a fad” and that they were shrinking the computer science department. “I was crushed,” Melinda says. Duke, which was expanding in computer science, got her instead. She earned her BA and MBA in five years. Then a helpful recruiter from IBM, where Melinda had worked as a summer intern, directed her to Microsoft. “I told the recruiter that I had one more interview—at this young company, Microsoft,” she recalls. “She said to me, ‘If you get a job offer from them, take it, because the chance for advancement there is terrific.'”

Dating the Boss

Arriving in Seattle in 1987 as a marketing manager for a predecessor of Word, Melinda, 22, was naive about what Microsoft held for her. “There were a lot of idiosyncratic people. They were all so smart, and they were changing the world,” she says, unfazed that she was the youngest recruit and the only woman among ten MBAs. The culture, though, did faze her. “It was a very acerbic company,” she recalls. That culture trickled down from the top, where Gates and Ballmer badgered and harangued managers. Melinda thought about leaving Microsoft.

 

But four months after she started, during her first trip to New York City, for the PC Expo trade show, she went to a group dinner and sat next to the CEO. “He certainly was funnier than I expected him to be,” she recalls. What attracted Bill to Melinda? “I guess her looks,” he says.

Later that fall, on a Saturday afternoon (“Everybody worked on Saturday,” she says), Melinda and Bill ran into each other in a Microsoft parking lot. “We talked awhile, and then he said, ‘Will you go out with me two weeks from Friday night?’ I said, ‘Two weeks from Friday? That’s not nearly spontaneous enough for me. I don’t know. Call me up closer to the day.'” Bill called Melindalater that day, rattling off his lineup of meetings and commitments. “I promised I would meet him later that night,” she says.

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The scrawny brainiac had just become a billionaire from Microsoft’s 1986 IPO. Yet even that kind of money can’t buy you love. Asked if Melinda played hard to get, Bill replies, “She was hard to get!” Both Melinda and her mother decided that dating the CEO was not a good idea. But, says Bill, “we found ourselves deeply emotionally connected.” Melinda was adamant that their relationship would not affect her work. “I wanted no public exposure. And I drew this line in the sand that I would never, ever, ever go to him on anything related to work.” She explains, “It reached the point that Bill would say to me, ‘You never tell me what you’re doing.'”

The CEO’s attention notwithstanding, Melinda French was a hotshot. In nine years at Microsoft she rose to general manager of information products (Expedia, Encarta, Cinemania) and oversaw 300 employees. Her record wasn’t perfect. Remember Microsoft Bob, the version of Word for people afraid of computers? That was Melinda‘s baby. (“Too cute,” she says.) But even on troubled projects, Melinda was seen as a strong team builder. Says Patty Stonesifer, Melinda‘s former boss at Microsoft and now CEO of the Gates Foundation: “No question, if she had stayed, she would have been on the executive team at Microsoft.”

Melinda worried about marrying Bill. “Bill had money,” she says. “To me, it was like, Okay, Bill has money. Big deal.” She saw what success was doing to him—robbing him of his privacy and a normal life. Both Melinda and Bill, in fact, questioned whether his conquer-the-world capitalist nature could co-exist with a family. “I thought, ‘What would it be like to be married to someone who works that hard?'”

A friend from Omaha juiced the relationship. On Easter Sunday in 1993, Bill and Melinda were visiting his parents at their vacation home in Palm Springs when he announced that it was time to head back to Seattle. They returned to their private jet. The pilot announced the route. Bill drew the shades. To distract Melinda he pulled out a jigsaw puzzle. (“Bill’s very good at complicated jigsaw puzzles, but she’s unbelievable,” Buffett says.) When the plane touched down and the doors opened, “There’s Warren with a bugle,” Melinda recalls. (This isn’t Seattle, Melinda. It’s Omaha!) As Buffett drove them to Borsheim’s, a jewelry emporium owned by Berkshire Hathaway, he kept ribbing: “Bill, there’s a metric of love here. I spent 6% of my net worth on Susie’s ring. I don’t know how much you love Melinda, but 6% is the yardstick in Omaha.” Bill, worth $7.3 billion by this time, inquired about sales per square foot while Melinda checked out the goods. “I said an emerald. Bill said a diamond is more appropriate,” she recalls. She chose a diamond scandalously shy of Buffett’s price target.

Around that time Bill and Melinda started talking about giving his money away. They both figured they would wait until Bill was in his 60s, despite flak he was getting about his miserliness. “He had been advised by lawyers and accountants that he should have a foundation,” recalls his father, “but he refused. He said he didn’t need another entity.” Melinda‘s wedding shower in December 1993 shifted the thinking. Bill’s mother, Mary Gates, who was fighting breast cancer at the time, read a letter she had written to Melinda. “From those to whom much is given, much is expected” was its essence. Mary Gates passed away the following June. Her message spurred the creation of the first Gates charity, the William H. Gates III Foundation. Bill’s dad ran it out of cardboard boxes in his basement.

Initially, Melinda recalls, the idea was to put laptops in classrooms—which was derided by many as a self-serving gesture by a software tycoon. But at the time, she was volunteering in a couple of schools in Seattle, and she realized that “there’s a much bigger problem” than a technology divide. She and Bill decided to take on education reform broadly, focusing on secondary schools. “The piece that looked so intractable and no one was touching was high schools,” she says.

Soon after their wedding came the calling to global health. Melinda read a front-page New York Times story about children in developing countries dying of diseases that most Americans have never heard of—rotavirus, which kills more than 500,000 children every year—and others like malaria and tuberculosis that barely exist in the U.S. “I thought, ‘This can’t be happening,'”Melinda says, and she attached a note to Bill. (“This is how we work,” she says. “We constantly put stuff on each other’s desks.”) Reading the article, Bill learned about the World Bank’s 1993 Development Report, which calculated the cost of these diseases. He got the 344-page document and read it several times. “That is not something I will do,” notes Melinda. “I learn in a different way. I learn experientially.”

Buffett’s Gift

“Yes, we’re a couple that has fun discussing fertilizer while we walk on the beach,” says Bill proudly. We are sitting in the chairman’s office at Microsoft, and Bill, in an armchair, is rocking forward and back—an old habit that Melinda has not broken. “Melinda is more scientific and reads more than 99% of the people you’ll ever meet,” he says. When the couple reviews grants (of the 6,000 or so requests that the foundation receives annually, they personally evaluate only those asking for $40 million or more), they typically meet in a study or hash out their views during long walks. They discuss grant requests without notes in front of them because, as Melinda says, “You’d better have it in your head. That’s a good discipline.”

Former President Bill Clinton, who paid tribute to Melinda at a Save the Children dinner in New York City in September, said that two years ago, when he went to Africa with the Gateses, he and Bill “thought we were so smart. We showed how much we knew about all these issues, you know, and we asked all the right questions. Melinda just sat there patiently. And then when we shut up, she bored in and said, ‘What are you doing in education? What are you doing on prevention? How many people are using condoms?'” The two Bills wilted. “Melinda showed that in the end, women are stronger than men when it counts,” Clinton said.

As Melinda has handed him AIDS babies with dirty pants, her husband has developed a noticeable compassion. But hers seems natural. Her close friend Charlotte Guyman, a retired Hewlett-Packard and Microsoft executive who is now on Buffett’s Berkshire Hathaway board, recalls a trip to Calcutta in 2004. One day, when Melinda had foundation meetings to attend, Guyman and a few in their group spent a half-day at Mother Teresa’s Home for the Dying. There, they were captivated by one young woman suffering from AIDS and tuberculosis who was “just bones,” Guyman says. No one could break the woman’s zombie-like stare. The next day Melinda visited. “Melinda walks in, pauses, and goes right over to this young woman,” Guyman recalls. “She pulls up a chair, puts the woman’s hand in her hands. The woman won’t look at her. Then Melinda says, ‘You have AIDS. It’s not your fault.’ She says it again: ‘It’s not your fault.’ Tears stream down the woman’s face, and she looks at Melinda.” Guyman can’t forget the connection. “Melinda sat with her. It seemed like forever.”

Seeing such suffering up close has led the Gateses to direct more money to what they call intervention: those bed nets, condoms, microbicides (clear, odorless gels that women apply vaginally) that help ward off illness and death until the magic bullet, vaccines, arrives. As AIDS among women has exploded in the developing world, Melinda, who goes to church regularly, feels no guilt about funding programs that more conservative Roman Catholics question. “Condoms save lives,” she says.

As mighty as the Gates Foundation is, Melinda insists that it needs partners. Relatively speaking, she says, “our pocket of money is quite small. The NIH budget is $29 billion. The state of California spends $60 billion in one year. If we spent that, our entire foundation would be out of business.” So the Gates Foundation has allied with other charities—Rockefeller, Michael and Susan Dell, Hewlett—and with companies such as GlaxoSmithKline and Procter & Gamble on various projects. The most successful joint venture is the GAVI Alliance, formerly called the Global Alliance for Vaccines and Immunization, which the Gateses helped start with donations of $1.5 billion. With 17 donor governments and the European Union in the fold, GAVI has distributed vaccines (including tetanus, hepatitis B, and yellow fever) to 138 million children in 70 of the world’s poorest countries. Thanks largely to this alliance, immunization rates are at all-time highs in the developing world, and more than two million premature deaths have been prevented.

Closer to home, where just 70% of American ninth-graders graduate on time from high school, reforming education has been a slog. Melinda admits that she and Bill were initially naive. “I thought that if we got enough schools started, people would say, ‘Let me build schools just like that.’ Just the opposite is true. You could get 1,000 schools up and running, and the system would pull them down.” In Denver and even in Seattle, the Gateses‘ backyard, some of their education efforts have failed for want of community engagement or the right leadership. So now theGateses are working with 1,800 high schools and aligning with superintendents, mayors, and governors wherever they can. “It’s always been one step forward and one step back,” Melindasays.

New York City, though, shows what Gates money can do. At 43 new small high schools funded by the Gates Foundation, graduation rates are 73%, compared with 35% for the schools they replaced. The Gateses‘ partner here happens to be Joel Klein, who led the government’s antitrust case against Microsoft a decade ago and now runs New York City’s public schools. Klein appreciates the irony of their alliance, calling the progress “a tribute to Bill.” For his part, Bill claims that it was no big deal to give his money to his former nemesis. And Melinda won’t say a word about the tension that stemmed from that period. “That’s part of our relationship that I need to keep private,” she says. But clearly she helped her husband get his head around the notion of working with Klein. “This is one of the great things about Bill,” she says. “Bill looks forward.” Buffett observes, “When Bill gave $50 million to New York City schools with Joel Klein in charge, I thought, ‘This guy can rise to the occasion.'”

Now, with another key partnership—the one with Buffett—the Gateses have more to spend and do than ever. Buffett had planned to hold onto his money until his death, but he changed his mind after his wife, Susie, died in 2004. In the spring of 2006, after lots of hinting, he broke the news to Bill. When Bill went home and told Melinda, they went on a long walk, and both cried. Melinda recalls, “We said to each other, ‘Oh, my gosh, do you know how responsible we’re going to feel giving someone else’s money away?'”

Buffett, who requires that the Gateses spend his annual contributions in full the following year, has given them just one piece of advice: “Stay focused.” He considers the Gateses “the perfect solution,” he says, because they are experts in philanthropy and also because he sees himself in Bill and his late wife in Melinda. “Bill is an awkward guy. He’s lopsided, but less lopsided since he’s with Melinda,” he says. “Susie made me less lopsided too.” Perhaps proving the point, Bill is quite touching when he explains his delight in disbursing Buffett’s billions. “Warren knows how lucky I am to have Melinda. It makes him look back at his time with Susie and wonder what it would have been like to be doing the giving with Susie.”

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Bill and Melinda are only now figuring out their new division of duties—crucial in a 500-person outfit that will probably double in size in two years. Bill, no organization geek (that would be Ballmer), intends to spend more time with scientists and academics, explore technology in education, and egg on the pharmaceutical companies that are not working on vaccines for the developing world. “Nobody gives them a hard time,” he complains. “That job is natural for me to do.” Melinda, meanwhile, intends to focus on personnel and culture. Some critics of the foundation contend that only managers who are close to the Gateses have the clout to get things done. Melinda says she wants to push decision-making further down the organization. Asked whether criticism about the Gates Foundation’s bureaucracy is valid, she replies, “You bet, some of it is.” Still, she says, “years ago we got compliments about how fast we reviewed grants. Those grants were swift, but they were not all as effective as they could have been. I’d rather be a bit more methodical and effective.” She also believes that the foundation must respond better to charges that its assets are invested in companies, including BP and Exxon Mobil, whose business interests can conflict with its altruistic goals. In May, Melinda and Bill directed endowment managers to divest stocks of companies invested in Sudan.

Housing Crisis

Melinda and Bill married on Jan. 1, 1994, in a small ceremony on the Hawaiian island of Lanai, with Willie Nelson, one of her favorite singers, performing—a surprise arranged by Bill. Afterward, Melinda says, she had “a mini sort of personal crisis.” This crisis was over the house Bill was building on Lake Washington outside Seattle. It was a bachelor’s dream and a bride’s nightmare: 40,000 square feet with several garages, a trampoline room, an indoor pool, a theater with a popcorn machine, and enough software and high-tech displays to make a newlywed feel as though she were living inside a videogame. “If I do move in,” she recalls telling Bill, “it’s going to be like I want it to be—our house where we have our family life.” After six months of discussions about shuttering the project, Melinda hired a new architect to redesign the place. They worked together to create intimate spaces, an office for her, and staff quarters out of sight and on the periphery.

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The couple moved in before construction was finished, which might have been a mistake. “Having a hundred workmen there gave her the message, ‘This is what your life is going to be like,'” Bill says. He used to tell Melinda: “Every day I want to hear one thing you like about this house.” She recalls: “I’d say, ‘Okay, I like the laundry chute.’ Or ‘Okay, here’s what I like and ten things I don’t like.'”

The house is, of course, a metaphor for Melinda‘s desire for normalcy. Her foremost concern is that the kids lead lives as normal as possible. She insisted on booting all hired help on weekends except for the security people and a sitter who arrives late in the day in case she and Bill want to exercise or go to dinner or a movie. Wednesday night is family swimming night. Friday night is family movie night. Bono, who has stayed with the Gateses several times, says, “That home has a stillness to it. It’s got a sort of Zen-like quality. Melinda has created that.” When they congregate in the light-filled kitchen overlooking the lake, Bono says, “they’re fun to hang out with. And they’re funny. She plays the straight man to his dark humor.”

Melinda appreciates Bono’s description. But does she like the house? “Now I like it,” she says, smiling. “I still wouldn’t build it. But I like it.”

The Gates children are reaching the age where they want to understand their parents’ passions. In 2006, Melinda and Bill took the two oldest children to South Africa, showing them slums and an orphanage in Cape Town. But the value of their work is often difficult to translate. A few years ago when they showed a documentary about polio, the kids asked about a crippled boy featured in the film: “Did you help that kid? Do you know the name of that kid? Well, why not?” On and on. “We don’t know that boy,” Melinda told the children, “but we’re trying to help lots of kids like him.” Bill’s explanation: “I’m in wholesale. I’m not in retail!”

As Bill says about their children, “They know the money is overwhelming.” And of course the kids have asked whether their parents will provide for them as generously as they do for those poor people who receive their billions. “We say, ‘You’ll be fine. You’ll still be very well-off,'” Bill says. While he and Melinda plan to give away 95% of their wealth in their lifetimes, they have not yet decided how much of what’s left will go to the children. Melinda says they will follow Warren Buffett’s philosophy: “A very rich person should leave his kids enough to do anything, but not enough to do nothing.”

“My fatal flaw?” Melinda says, laughing, during our third and final interview. She sometimes wishes for a simpler life, she admits. “It depends when you catch me. Most days, no. But if you’d asked me yesterday if I would like a much simpler life, I would have told you yes.” Yesterday was that night before the Malaria Forum, when she went to bed feeling unprepared. This morning, as she sat onstage and scrutinized the audience of renowned doctors and health experts, she says, “I was telling myself, ‘I know that person … I know his work … I know her work.'” She was giving herself a pep talk. “I told myself, ‘But I do know enough.'” She completed her goal for the day: calling for the eradication of one of the worst diseases the world has ever known. Tomorrow, another goal. Maybe it will be even bigger.

This article was originally published in the January 21, 2008 issue of Fortune.