Disheartening results and less than dazzling forecasts prompted a sell-off in several sectors, notably health care and technology. Analysts said investors were feeling let down after a month of bidding stocks higher in anticipation of a robust quarter.

"We’ve had plenty of reason for profit-taking, and it’s all because of these earnings," said Todd Clark, head of listed equity trading at Wells Fargo Securities. "We had a pretty nice rally and now people are looking to take their money off the table."

The Dow lost 149.40, or 1.5 percent, to close at 9,598.24, its biggest one-day point decline since it fell 150.53 on Sept. 24.

The broader gauges also fell sharply. The Nasdaq composite index dropped 42.83, or 2.21 percent, to close at 1,898.07, its biggest drop since it fell 58.02, also on Sept. 24.

The Standard & Poor’s 500 index shed 15.67, or 1.5 percent, to close at 1,030.36. The index also had its largest drop since Sept. 24, when it fell 19.65.

Overall, the more than 200 companies that reported earnings in the last two weeks have either met or beaten analysts’ expectations, but investors have dumped stocks on hints of negativity — including dimming outlooks for the fourth quarter and next year. The market’s sharp response to today’s reports suggests fund managers may be trying to book profits, said Scott Wren, equity strategist for A.G. Edwards & Sons.

"When I see a market reaction like this today, it’s telling me there’s some churning in some big accounts," Wren said. "People have a pretty quick trigger finger these days."

Analysts blamed some of the decline in the Dow on a disappointing report from Merck & Co. Large pharmaceutical companies, which investors depended on for predictable earnings during the economic downturn, are likely to lose their appeal during the recovery, said Kevin Caron, market strategist at Ryan, Beck & Co.

"Investors have come to rely on pharmaceuticals for growth in revenue and pipeline, but those growth rates are slowing," said Caron, whose firm reduced its stake in health care last month in favor of technology, industrial and material goods stocks. "That’s going to be an additional challenge for those companies going forward."

One winner today was McDonald’s Corp., which beat analyst expectations by 3 cents a share largely on the success of its entree-sized salads, McGriddles breakfast sandwiches and extended hours at its U.S. restaurants. The fast food chain closed up 16 cents at $23.90.