Stocks mostly gained Tuesday as Merck & Co.'s boosted profit outlook and a dividend increase from IBM Corp. helped lift equities while the Federal Reserve meets. The only index to fall was the Nasdaq composite.

At the close on Wall Street, the Dow Jones industrial average was up 72.2 points, about 0.4 percent at 18,110.1. The Standard & Poor's 500 index gained 5.8 points, about 0.3 percent, to close at 2,114.8. The Nasdaq composite lost 4.8 points, about 0.1 percent, ending the day at 5,055.4.

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ENERGY: As the market closed, benchmark U.S. crude lost 9 cents to $56.90 a barrel in trading on the New York Mercantile Exchange. Brent crude fell 8 cents to $64.73 a barrel in London.

Merck added 5.6 percent after the drugmaker lifted its annual earnings forecast.

International Business Machines Corp. climbed 2.3 percent. Twitter Inc. fell 5.8 percent after Selerity Inc. unexpectedly reported the company's results. The stock was halted and Twitter later released earnings that topped estimates and cut its annual forecast.

Earnings are "driving most everything that's going on right now," said analyst Tom Wirth, senior investment officer for Chemung Canal Trust Co., which manages $1.9 billion in Elmira, New York. "When I look at the stocks that are doing well and those that aren't doing so well, it's mostly earnings driven here."

In addition to reviewing the corporate earnings reports, investors are also awaiting the outcome of the Federal Reserve's two-day meeting, which ends Wednesday, for more clues on the timing of interest rate increases.