U.S. companies are holding more cash in the bank than at any point on record, underscoring persistent worries about financial markets and about the sustainability of the economic recovery.

The Federal Reserve reported Thursday that nonfinancial companies had socked away $1.84 trillion in cash and other liquid assets as of the end of March, up 26% from a year earlier and the largest-ever increase in records going back to 1952. Cash made up about 7% of all company assets, including factories and financial investments, the highest level since 1963.

While renewed confidence in corporate-bond markets has allowed big companies to raise a record amount of money, many are still hesitant to spend the cash on hiring or expansion amid doubts about the strength of the recovery. They are also anxious to keep cash on hand in case Europe's debt troubles lead to a new market freeze.

"Cash is still king," said Jeff Hand, chief operating officer at Ross Controls, a Troy, Mich., maker of pneumatic valves and other products that is holding more cash as it struggles to recover from a sharp drop in business last year. "We're coming out of that, but the uncertainty is still there."

The rising corporate cash balances could represent a longer-term behavioral shift in the wake of the deepest financial crisis in decades. In the darkest days of late 2008, even large companies faced the threat that they wouldn't be able to do the everyday, short-term borrowing needed to make payrolls and purchase inventory.

"We just went through this liquidity crunch that's made them realize the value of a dollar in hand," said John Graham, an economist at the Duke Fuqua School of Business.

Even now, banks continue to pull back on lending. The Fed reported Thursday that net lending by the financial sector—including banks, credit unions and other lenders—was down 5.4% in March from a year earlier.

The comfort of having cash on hand, though, comes at a high price companies may not be willing to pay for much longer. They are earning almost no interest on their holdings of cash, making it more difficult for them to achieve the returns shareholders typically expect from them. That will put pressure on companies to pare down the cash holdings eventually.

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In a recent survey of company chief financial officers that Duke's Mr. Graham conducted with CFO Magazine, he found that companies expect capital spending to increase by 9% over the next year, compared with 1.5% when he asked the question in December. They expect employment to grow by 0.7%, compared with the 1.4% drop they expected six months ago.

Companies' willingness to use their cash will play a major role in the strength of the recovery at a time when consumers need jobs to support their spending and many people are still trying to repair their finances.

The Federal Reserve data showed households making some progress in paring down their debt, which fell at a 2.5% annual rate in the first quarter as credit remained tight and more homeowners defaulted on their mortgages.

Household net worth—the value of houses, stocks and other investments, minus debts—rose for a fourth straight quarter as markets continued to rebound. At $54.6 trillion, though, it was still $11.3 trillion below its 2007 peak of $65.9 trillion.