The bumpy trading Thursday came after the Federal Reserve decided to keep interest rates low, citing weakness in the global economy and unsettled financial markets.
Bond prices rose, sending yields lower, as traders reacted to the Fed's prediction that inflation will remain subdued. The dollar fell against other currencies.
The Dow Jones industrial average ended down 65 points, or 0.4 percent, at 16,674. It rallied shortly after the Fed's statement came out, then drifted lower for the rest of the day.
The Standard & Poor's 500 gave up five points, or 0.3 percent, to 1,990 and the Nasdaq rose four points, or 0.1 percent, to 4,893.