Stocks slipped Monday in one of the quietest trading sessions of the year. Worries about European debt crept up again, and Apple became the most valuable company of all time.
The Dow Jones industrial average fell 3.56 points, or 0.3 percent, at 13,271.64. The Standard & Poor's 500 fell a sliver, 0.03 point, to 1,418.13. The Nasdaq composite index fell 0.38 point to 3,076.21.
With many traders and investors on vacation, volume on the New York Stock Exchange was light, just 2.7 billion shares traded. The average this year is about 1 billion more.
In a monthly report, the German central bank reiterated doubts about having the European Central Bank buy bonds to help struggling European economies. It stressed that such purchases could carry "substantial risks."
Earlier this month, stocks rallied after ECB President Mario Draghi said the bank might buy bonds of some European countries to lower their borrowing costs. German Chancellor Angela Merkel also seemed to soften her stance on the idea.
"We're getting mixed messages at best coming from Europe," said Jim Russell, chief equity strategist at U.S. Bank Wealth Management. "Investors are on the sidelines, and they're still a little scared."
Apple, the most valuable company in the world, became the most valuable in history. It hit a market value of $623 billion, surpassing Microsoft's record from 1999. Apple is worth almost twice as much the next most valuable company, Exxon Mobil.
Apple stock rose $17.04, or 2.6 percent, to $665.15.
Stocks had been inching up for six weeks. On Friday, both the Dow and the S&P closed just below four-year highs.
Monday's drop was the 11th trading day in a row of moves of less than 1 percent for the S&P, according to FactSet, a financial data provider. In same period last year, amid fears the U.S. would default on its debt and a possible second recession, the S&P moved up or down by 1 percent or more roughly every other day.
Other stocks moving sharply Monday included Lowe's, the world's No. 2 home improvement store. It missed earnings expectations and lowered its outlook for the year. The stock fell 6 percent.
The health insurer Aetna announced it would buy Coventry Health Care for $5.7 billion as the insurance industry realigns itself to better navigate the health care overhaul. Aetna rose $2.14, or nearly 6 percent, to $40.18. Coventry climbed $7.10, or 20 percent, to $42.04.
The deal follows the $4.46 billion buyout last month of another insurer by WellPoint Inc., and last year's acquisition worth nearly $4 billion by Cigna of HealthSpring as it grabbed for a share of Medicare revenue.
Best Buy slid 10 percent after rejecting an offer from its founder and largest shareholder to take the electronics retailer private. The company named Hubert Joly, the former head of global hospitality company Carlson and a turnaround expert, as CEO Monday.
Facebook gained 96 cents, or 5 percent, to $20.01, following a slide last week after some insiders were able to sell stock for the first time since the company's public trading debut in May at an offering price of $38.
In the S&P 500, six of the 10 main industry groups fell, led by a 0.8 percent drop in telecommunicationsstocks.
In Europe, stocks fell. Greek stocks fell 2 percent. Spain's main index was off 1 percent.
Investors are on edge this week because of a series of meetings among European leaders to discuss the debt crisis. The first came Monday when the Greek foreign minister met with his German counterpart in Berlin to discuss Greek spending cuts necessary for the country to continue receiving bailout money.