Fears that the global economic recovery has stalled pushed the Dow Jones industrial average below 12,000 for the first time since March and drove the stock market lower for the sixth straight week.
Friday's drop extended the longest weekly losing streak for stocks since the fall of 2002.
Bad economic news has dampened hopes for a steady recovery. Traders worry that weaker hiring, sluggish industrial output, and a moribund housing market are reversing a bull market that lifted the Dow 20 percent over the last year.
The Dow fell 172.45 points, or 1.42 percent, to close Friday at 11,951.91. The S&P 500 index fell 18.02, or 1.40 percent, to 1,270.98. The Nasdaq dropped 41.14, or 1.53 percent, to 2,643.73.
Shares had bounced back Thursday, breaking six straight days of losses, after U.S. exports unexpectedly hit a record in April. By Friday morning, those gains had evaporated. The losses were widespread, with declines in all 10 of the S&P 500's industry groups.
Aside from the report on higher exports Thursday, investors had little reason to cheer this week. Citigroup Inc., Bank of America Corp., and other big banks led stocks lower Monday amid expectations that banks would have to set aside more cash to cover potential losses.
Federal Reserve Chairman Ben S. Bernanke gave a speech Tuesday in which he said the economy's greatest troubles - high oil prices and supply-chain disruptions from Japan - would soon pass. He offered no hint of further help from the Fed, and the stock market dropped as he spoke. The next day, stocks slipped again after a Fed report showed the economy slowed in New York, Chicago, and other major metropolitan areas.
The euro fell below its recent highs on signs that European policymakers have reached an impasse over how to handle Greece's drawn-out debt crisis.
In corporate news, shares of the solar chip maker MEMC Electronic Materials Inc. fell 3.5 percent after an analyst downgraded the stock, saying prices for solar wafers are falling rapidly because of overproduction in China.