U.S. stocks had their worst one-day drop since February as traders worried about weak corporate earnings and the looming end of economic stimulus from the Federal Reserve.
The drop interrupted a prolonged advance in the market and erased its gains for July. It was only the second monthly loss for stocks this year, after January.
The Dow Jones industrial average plunged 317 points, or 1.9 percent, to close at 16,563 Thursday.
The Standard & Poor's 500 index dropped 39 points, or 2 percent, to 1,930. The Nasdaq composite dropped 93 points, or 2.1 percent, to 4,369.
The S&P 500 closed at a record high just one week ago.
Whole Foods Market, Yum Brands and Exxon Mobil were among companies that fell after reporting results or forecasts that disappointed investors.