Computer company Dell, American Airlines and US Airways and food giant Heinz have all been involved in major deals this week. Even if these deals don't all survive to completion, mergers are viewed by many as a sign of corporate confidence and financial health.
Rumors about Walmart's February sales figures weighed heavily on the Dow Jones industrial average as the company's shares dropped 3 percent, analysts said.
The DJIA was up 8.37 points or 0.06 percent to 13,981.76 after a day of choppy trading.
The Nasdaq composite index shed 6.63 points or 0.21 percent to 3,192.03. The Standard and Poor's 500 lost 1.59 points or 0.10 percent to 1,519.79.
On the New York Stock Exchange, there were 1,489 advancers to 1,550 decliners on a composite volume of 3.8 billion shares
The 10-year treasury note fell 4/32 to yield 2.015 percent.
Against the dollar, the euro held steady at $1.3362. The dollar rose to 93.52 yen from 92.87 yen.
The Nikkei 225 index in Tokyo lost 1.18 percent, 133.45 points, to 11,173.83.
In London, the FTSE 100 index added 0.01 percent, 0.90 points, to 6,328.26.