The 10 biggest health-care companies in the Fortune 500 by Laura Lorenzetti @FortuneMagazine June 20, 2015, 9:25 AM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons For companies in the health-care industry, 2014 was an exceptionally busy year, as companies adapted to new Affordable Care Act regulations and sought new partners in a pharmaceutical and biotech mergers-and-acquisition spree. Some companies in the sector have taken advantage of the changes and rocketed up the Fortune 500 list, including AmerisourceBergen, which moved to No. 16 from No. 28, and Aetna, which went to No. 49 from No. 57. Others, like UnitedHealth Group and Anthem, have held steady. But for the most part, the health-care behemoths rode the wave of change, finding ways to maintain or improve sales amid a fast-changing landscape. The fact that all 10 of these firms are in Fortune’s top 50 speaks volumes about the dominant role health care plays in the U.S. economy. (You can explore the full list here, in its new, sortable online version.) Here are the 10 biggest health-care companies from this year’s Fortune 500 list, as measured by revenue.