Stocks finished a historic month of gains on a sour note, as concerns about the plan to stave off Europe's debt woes drove a selloff.
The Dow Jones Industrial Average shed 276.10 points, or 2.3%, to 11955.01. All of the Dow's 30 components fell on Monday. Despite the losses, the blue-chip measure finished October up 9.5%, its third-biggest monthly percentage gain in its 115-year history.
The Standard & Poor's 500-stock index slid 31.78 points, or 2.5%, to 1253.31, led lower by energy, material and financial stocks. October is the first month the index has gone without two consecutive days of declines since October 2006.
The technology-oriented Nasdaq Composite dipped 52.74 points, or 1.9%, to 2684.41.
"Doubt seems to be creeping back into the market," said Jim Dunigan, managing executive of investments at PNC Wealth Management. "You're not going to solve Europe's problems by waving the magic wand and expecting it to be over."