Europe's banking troubles and an impasse over lifting the U.S. government's borrowing limit dragged down stock markets in the U.S. and Europe. Gold rose above $1,600 an ounce as investors sought safe places to park money.
The results of stress tests on European banks came under more scrutiny. Eight banks failed the test to measure how well they would hold up under additional financial strain. But the tests didn't take into account how banks would fare if Greece or Italy defaults. Greece and Italy are among the countries most at risk of default.
The Dow Jones industrial average and the Nasdaq composite index lost their gains for the month.
The Dow Jones industrial average fell 94.57, or 0.8 percent, to 12,385.16.
The Standard and Poor's 500 fell 10.70, or 0.8 percent, to 1,305.44.
The Nasdaq composite fell 24.69, or 0.9 percent, to 2,765.11.
For the year to date:
The Dow is up 807.65 or 7.0 percent.
The S&P is up 47.80 or 3.8 percent.
The Nasdaq is up 112.24, or 4.2 percent.