Stocks mostly fell on Monday as energy shares sold off on lower oil prices and the onset of earnings season was clouded by concern company outlooks may fall short of expectations.

Worries that increased raw material costs and the effects from Japan's earthquake may affect coming quarters will put companies' forward-looking statements under increased scrutiny.

Companies are going to be trying to dampen expectations for the second quarter, said Subodh Kumar, chief investment strategist at Subodh Kumar & Associates in Toronto. The market focus is more internal as to whether it's gone up too fast.

After the bell, Alcoa Inc reported a first-quarter profit that beat estimates and said its outlook for the rest of 2011 and beyond remains positive. But revenue of the aluminum maker, the first Dow component to report quarterly results, missed forecasts and the stock fell 3.6 percent to $17.13 in post-market trade.

Energy shares fell as U.S. crude futures slid on profit-taking. Occidental Petroleum fell 3.2 percent to $100.42 while the S&P energy index <.GSPE> fell 1.9 percent.

Profits for S&P 500 companies are seen rising 11.4 percent from a year ago, according to Thomson Reuters data, but much of that may be priced into shares. The S&P 500 is up over 5 percent this year.

Optimism over earnings contributed to recent gains, despite turmoil in oil-producing regions and the disasters in Japan. Despite the S&P 500's gains this year, light trading volume has prompted questions about the strength of the rally.

The Dow Jones industrial average <.DJI> rose 1.06 points, or 0.01 percent, at 12,381.11. The Standard & Poor's 500 Index <.SPX> fell 3.71 points, or 0.28 percent, at 1,324.46. The Nasdaq Composite Index <.IXIC> lost 8.91 points, or 0.32 percent, at 2,771.51.

U.S. crude oil futures ended 2.5 percent lower after a recommendation from top brokerage Goldman Sachs to take profits after the recent rally triggered a sell-off.

In corporate news, Tenet Healthcare Corp said it has sued its suitor, Community Health Systems Inc , claiming the rival hospital operator admitted patients for unneeded stays to overbill insurers, including Medicare.

Shares of Tenet sank 14.7 percent to $6.44 while Community slumped 36 percent to $25.89.

NYSE Euronext on Sunday rejected a joint buyout bid from Nasdaq OMX Group and IntercontinentalExchange and said it was sticking with an earlier bid from Deutsche Boerse AG . Nasdaq reaffirmed that its offer was superior to Deutsche Boerse's lower offer.

NYSE shares fell 2.9 percent to $37.59 while Nasdaq OMX fell 1.5 percent to $28.03 and ICE was unchanged at $120.55.

Also in deal news, Endo Pharmaceuticals Holding Inc said it would buy American Medical Systems Holdings Inc for about $2.6 billion while Level 3 Communications Inc agreed to buy Global Crossing Ltd for $1.9 billion in stock.

Endo rose 0.5 percent to $41.06 while American Medical jumped 32 percent to $29.50. Level 3 rose 18.1 percent to $1.70 and Global Crossing surged 69 percent to $24.97.

Biogen Idec Inc rose 7.2 percent to $78.55 and was the top percentage gainer on the Nasdaq 100 <.NDX> after the company's experimental multiple sclerosis drug met the main goal in the first of two important late-stage studies.

Composite volume was light on the NYSE, Amex and Nasdaq with 6.73 billion shares changing hands compared to last year's daily average of 8.47 billion.

Declining stocks outnumbered advancing ones on the NYSE by about 5 to 2, while on the Nasdaq about two shares fell for every one that rose.

(Editing by Leslie Adler)

Fall Energy