The Dow Jones industrial average fell 213.66 points, its biggest decline of the year and third triple-digit loss in four days. It closed at 12,715.93, its lowest since Feb. 2.
A five-day losing streak has shaved about 550 points off the Dow, about half what it gained from January through March.
In Europe, concern about the financial health of Spain intensified, and borrowing costs for both Spain and Italy rose considerably. Spain's borrowing costs crept closer to levels that forced other countries to seek bailouts.
European markets sold off while Wall Street was still sleeping. The main stock indexes in Spain and France closed down about 3 percent, the equivalent of a 400-point drop in the Dow. Stocks dropped 2.5 percent in Germany and 2.2 percent in Britain.
"They've managed to put a Band-Aid on the debt crisis, but there's really no solution," said Colleen Supran, a principal at the investment adviser Bingham, Osborn & Scarborough. "And Spain is a much bigger problem than Greece."
The yield on 10-year Spanish bonds rose to almost 6 percent. The point at which governments can no longer afford to raise money on the international bond markets and must seek bailouts is generally considered to be 7 percent.
The 7 percent level forced Greece, the last focal point of the European debt crisis, to seek rescue loans. But Spain's economy is more than five times as large as Greece's.
In the United States, investors waited for an earnings report from Alcoa, the aluminum maker, scheduled for just after the closing bell. Alcoa is the first of the 30 stocks in the Dow to report its quarterly results.
After nine consecutive quarters of earnings growth, analysts think earnings will be flat this time. Better performance than that could stop the market's decline, but a weaker showing could accelerate the selling.
Alcoa stock fell 2.9 percent ahead of the report, compared with a 1.7 percent decline for the broader Standard & Poor's 500.
"Whatever qualifications you want to give it — it's because of cost-cutting, they've laid off a lot of people — earnings have been one bright spot," said Adrian Day, president of Adrian Day Asset Management in Annapolis, Maryland. "If that were to turn, that would be sort of the last leg on the stool being knocked away."
After the strongest first three months for stocks since 1998, investors have found plenty to fret about.
The losing streak began last Tuesday, when the Federal Reserve said it was worried about the strength of job growth and suggested it was not inclined to provide further help for the economy.
The Dow fell 204 points in three days. It fell 131 more on Monday, the first time investors could react to a report showing much weaker job growth in March than in the three previous months.
Then, on Tuesday, the National Federation of Independent Business reported a drop in its small-business optimism index, the first decline after six months of gains.
That report helped knock stocks down at the open, and with Europe to worry about, they sank all day. The S&P finished down 23.61 points, its worst one-day decline this year, at 1,358.59.
The Nasdaq composite index, which eked out a gain in one of the past four days, ended down 55.86 points, its worst performance this year, at 2,991.22. It closed below 3,000 for the first time in a month.
Consumer discretionary stocks, which include travel companies, clothing stores and cable companies, fell 2.4 percent as group, the worst-performing segment of the market.
Financial stocks fell almost as much, and even utilities and health care stocks, which are more dependable in times of economic uncertainty, were down more than 1 percent each.
The worst-performing stock in the Dow was Bank of America, which tends to take a hit when concerns about Europe grow stronger. Bank of America was down 4.4 percent.
Trading was the most active since March 16, 4.6 billion shares.
Last year, the Dow's longest losing streak was an eight-day, 858-point plunge in July and August, with Congress bickering over the government debt limit and just before the S&P ratings agency downgraded the U.S.
On Tuesday, the dollar and U.S. Treasury prices rose as investors shifted money into lower-risk investments. The yield on the benchmark 10-year Treasury note fell for the fifth straight day, dropping to 1.99 percent from 2.04 percent Monday.
When earnings reports begin rolling in, analysts think they will reflect slowing growth in China and a tottering Europe. But "a lot of these companies are in a good spot," said JJ Kinahan, chief derivatives strategist for TD Ameritrade in Chicago.
"There seems to be this black cloud as everyone talks about the market," Kinahan said.
He noted that stocks are still well ahead for the year. The S&P 500 was up 8 percent even counting Tuesday's decline. The Dow was up more than 4 percent and the Nasdaq 15 percent.
The low expectations for earnings could also be a blessing in disguise. Companies may have an easier time beating them, which can drive up their stock price, at least temporarily.
"CEOs have done a very good job of setting expectations low," Kinahan said.
Analysts have also worried that high gasoline prices could hurt the economic recovery. The price of oil fell almost to $101 a barrel Tuesday, but that was because traders are betting that a weak U.S. economy will keep demand low.
Oil was about $75 in October. The buildup has been partly because of tension over Iran's nuclear program and the oil embargos that have ensued. It nearly hit $110 last month.
