The selling wiped out all of the gains from yesterday's rally. Analysts, attributing the volatility to Wall Street's lack of confidence, said that until business conditions show solid improvement, investors will sell their stocks as soon as they make even a small profit.

"An upswing has to be driven by better profits and increased corporate spending. That has yet to happen," said Subodh Kumar, chief investment strategist for CIBC World Markets.

The Dow closed down 155 at 9,126.82, according to preliminary calculations, after rising as much as 131 points in earlier trading. It was the average's fourth triple-digit decline in five sessions, for a total point loss of 579.30 since Wednesday.

The technology-focused Nasdaq fell 36.35, or 2.5 percent, to 1,423.99 ­ less than a point above its Sept. 21 finish of 1,423.19, its lowest close following the terror attacks.

The Standard & Poor's 500 index lost 16.58, or 1.7 percent, closing at 976.14.

The S&P is fewer than 10 points above its Sept. 21 low, while the Dow has 891 points to go.

Wall Street started the session with an advance as investors sought to extend a modest rally yesterday that gave the three indexes their first win in a week. Word of more orders at Boeing and improving sales at DuPont helped push stocks higher.

But the effort quickly faded on mixed economic news.

The Conference Board reported consumer confidence fell to a four-month low in June amid concerns about job security and uneasiness about corporate accounting scandals. Consumer spending accounts for two-thirds of the economy, and many strategists say a strong consumer is key to a business recovery.

Profit-taking intensified throughout the day as investors decided they were better off locking in their gains, particularly in technology. Cisco Systems dropped 61 cents, or 4.3 percent, to $13.45. Lucent tumbled 31 cents, or 13.6 percent, to $1.97 on a downgrade by Morgan Stanley, compounding a selloff yesterday on critical comments by UBS Warburg.

With second-quarter earnings reports due out next month, many investors are reluctant to make any new commitments. They want to see whether those numbers, along with any forecasts for the future, indicate whether the market will recover this year.

Federal Express fell $8.02 to $48 today after beating quarterly estimates, but offering estimates for the current quarter below many analysts' projections.

Among the handful of winners, Boeing closed up 13 cents at $42.87 on news it expects an increase in production of commercial aircraft in 2004. DuPont gained 13 cents to $43.24 after the chemical company increased its quarterly forecast citing strong sales.

Rite Aid rose 13 cents to $2.68 after the drug store chain reported a narrower-than-expected quarterly loss.