There was no letup in the flight from stocks and bonds as traders reacted to news that the Federal Reserve could end its massive bond-buying program as next year and as China's manufacturing slowed.
The Dow Jones industrial average plunged 354 points, or 2.3 percent, to 14,758 points Thursday.
The Dow has lost 560 points in the past two days, wiping out its gains from May and June.
The Standard & Poor's 500 dropped 40 points, or 2.5 percent, to 1,588. The Nasdaq fell 78 points, or 2.3 percent, to 3,364 points.
The price of gold dropped and bond yields rose sharply.
Stocks fell across the board. Twenty stocks fell for every one that rose on the New York Stock Exchange. Trading was very heavy at 4.8 billion shares.