FORTUNE — Some are worried that, at least in one part of the lending sector, we may now have the opposite of a crunch. Call it a credit stretch.

In the past three years, banks have upped their lending to businesses by $415 billion, according to That increase is far larger than it is for any other lending category. Nearly two-thirds of the increase in lending since the financial crisis has been to businesses.

And the jump in business lending is nearing what we had in the run-up to the financial crisis. Back then, corporate credit rose by $456 billion over the course of three years to a peak of $1.5 trillion in the fall of 2008 — a peak that we are now past.

Banks had nearly $1.6 trillion in outstanding business loans at the end of 2013, and it is likely up from there. As a percentage, business lending is up 35% in the past three years. The next-fastest-growing category over the same period was auto loans, which some are worried about as well; that category was up by $70 billion, a 25% jump.

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At the nation’s biggest banks, business lending is up even more. Bank of America BAC has upped its corporate lending by 40% in the past three years.

On top of that, a record $1.5 trillion in corporate debt was sold to investors in 2013.

All told, U.S. corporations had $14.9 trillion dollars in debt at the end of last year, according to the Federal Reserve’s flow of funds data, which was released on Thursday. That’s up from just under $13 trillion four years ago.

“I am deeply worried about the potential risk of the recent massive growth in C&I [commercial and industrial] loans,” says Bill Moreland, who runs Bankregdata. “Massive amounts of new lending, regardless of type or lender, inevitably result in subsequent waves of increasing delinquencies.”

Regulators seem concerned as well. Starting in the middle of last year, the Office of the Comptroller of the Currency, the Federal Deposit Insurance Corp., and the Federal Reserve began to question banks’ business-lending portfolios. Regulators are particularly concerned about business loans to less creditworthy borrowers. Rates have come down on so-called leveraged loans, and many now come with few restrictions on how much companies can borrow, what they can use the money for, and how much cash they have to hold in reserve.

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In part, the big jump in corporate lending is a result of the steep drop in the credit crunch. But the jump is odd given that loans to consumers have barely increased from the depths of the crisis.

Mortgage lending in 2013, for instance — by far the largest category of consumer debt — was up just under 3% since 2010. And most people expect home-lending activity to shrink in 2014. Credit card lending was up by just under 5%. Debt for new construction was down nearly 30%. Overall, bank lending remains weak. A key gauge of this market — loans to deposits — hit a new low at the end of 2013.

Still, it seems like good news that lending is up somewhere, unless, of course, the news is too good.