U.S. stocks slipped at the open on Monday following six weeks of gains on the S&P 500, but Aetna's purchase of rival insurer Coventry Health Care for $5.7 billion showed companies still see value in the market.
The Dow Jones industrial average fell 19.51 points, or 0.15 percent, to 13,255.69. The S&P 500 Index dipped 1.47 points, or 0.10 percent, to 1,416.69. The Nasdaq Composite shed 3.81 points, or 0.12 percent, to 3,072.78.
Healthcare was the best performing of the S&P 500 top 10 sectors in early trading.