Traders shoveled money into bonds, a signal they see weakness in the economy ahead.
The price of oil fell 3.8 percent as OPEC leaders gathered to discuss production cuts, which traders suspect may not reverse a plunge in crude.
The Dow fell 638 points, or 2.5 percent, to 24,392.
The S&P 500 index lost 61 points, or 2.3 percent, to 2,638. The Nasdaq dropped 117 points, or 1.7 percent, to 7,040.
The yield on the 10-year Treasury fell to 2.84 percent.