The Dow Jones industrial average is down 307 points, or 2.7 percent, to 10,933.
The Dow gave back much of its gain from Tuesday, when it surged 429 points after the Federal Reserve pledged to keep its key interest rate at nearly zero into 2013.
But the Fed's statement also included a dim outlook on the economy. It said growth has been "considerably slower" than it expected and that it anticipates a slower pace of recovery.
The S&P 500 is down 32, or 2.7 percent, to 1,141 in early trading. The Nasdaq is down 74, or 3 percent, to 2,409.
But Treasury issues are rising. The yield on the 10-year Treasury note fell to 2.15 percent from 2.26 percent late Tuesday.