Investors, worried about the health of the financial system and the survival of Detroit's Big Three automakers, pushed the Dow down 427.47 points, or 5.07 percent.

Broader indexes dropped even more - and the overall market closed at a value below $10 trillion for the first time since April 2003, Wilshire Associates said.

"Hideous day," said Bill Stone, chief investment strategist at PNC Wealth Management in Philadelphia. "It's hard to put a basement on this thing."

A cascade of selling occurred in the final minutes of the session as investors yanked money out of the market. For many, the real fear is that the economic slowdown might be even more protracted if the federal government does not bail out the troubled auto industry.

Investors also scoured economic data that included minutes from the last meeting of the Federal Reserve in which policymakers lowered projections for economic activity this year and next. Economic worries caused across-the-board selling, with financial stocks particularly hard hit.

In the minutes, released yesterday, the Fed signaled that additional interest-rate reductions may be needed to help combat the worst financial crisis to jolt the country in more than a half-century.

The day's losses on the New York Stock Exchange were staggering: Only 158 companies that trade there finished the day with gains, while 2,943 declined. Volume again was light, a symptom of the market's recent volatility, with 1.63 billion shares exchanging hands by the close.

Another sign of volatility: Since Sept. 15, when Lehman Bros. Holdings Inc. declared bankrupcty and Merrill Lynch & Co. Inc. rushed into the arms of Bank of America Corp. for survival, 42 trading days have seen the Dow rise or fall by triple digits. On just six days in that period, the gain or loss was less than 100 points.

Analysts expect the volatility to continue.

"I don't know what the catalyst is going to be where we turn the corner and people start buying stocks wholeheartedly again," said Jon Biele, head of capital markets at Cowen & Co. in New York.

For the year so far, the Dow has lost 40 percent. The Standard & Poor's 500 index is off 45 percent, and the Nasdaq composite is down 48 percent.

Yesterday's retreat in the United States followed declines in European and Asian stock markets. In the United States, concern mounted that the economic slowdown would cut profits at financial firms and commodity producers.

The Dow industrials closed yesterday at 7,997.28.

The S&P 500 fell 52.54, or 6.12 percent, to 806.58. The Nasdaq composite lost 96.85, or 6.53 percent, finishing at 1,386.42. Both closed at their lowest levels since March 2003 and were rapidly approaching the lows of the 2000 to 2002 bear market.

The Russell 2000 index of smaller companies gave up 35.13, or 7.85 percent, to 412.38.

Shares of Lincoln National Corp. plunged 40 percent yesterday, the steepest decline in the S&P 500, to $7.31. The Philadelphia life insurer said it expected a charge of as much as $300 million because of declining equity markets last month. Insurers in the S&P 500 lost 11 percent collectively.

Already hit hard by severe losses on their investment portfolios, insurance companies nationwide continue to face challenges as they try to convince investors that their capital reserves are safe.

Investors were rattled on prospects that General Motors Corp., Ford Motor Co., and Chrysler L.L.C. might not get a $25 billion rescue package before Congress quits for the year.

Ford shares, which traded as high as $8.79 in the last year, yesterday plunged 42 cents, or 25.00 percent, to $1.26. GM, a stock worth $29.95 in the last 52 weeks, fell 30 cents, or 9.71 percent, to $2.79. Chrysler is privately owned.

Citigroup Inc. tumbled 23.44 percent to $6.40, a 13-year low, after the bank said it would buy $17.4 billion of troubled investment-fund assets.