NEW YORK — Investors retreated yesterday, sending stocks moderately lower as existing home sales slid and volatile oil prices intensified Wall Street's summer malaise.

The Dow Jones industrial average fell 50.31, or 0.48 percent, to 10,519.58. Broader stock indicators also were down.

Bonds rose as stocks fell, with the yield on the 10-year Treasury note at 4.18 percent, down from 4.22 percent late Monday. The U.S. dollar was down against other major currencies.

Traders also worried as oil prices first rose, then fell. The volatility did not please equity investors, who are concerned that higher gasoline prices are curbing consumer spending. On Saturday, Wal-Mart Stores Inc., the world's largest retailer, said its third-quarter results would miss analysts' expectations due to rising oil prices. A barrel of light crude settled at $65.71, up 6 cents, on the New York Mercantile Exchange.

"We started the year at $42 a barrel oil— that was a concern, but we could get past it," said David Sowerby, chief market analyst, Loomis, Sayles & Co. "When we crossed $60, I don't think anyone could question what $60 is going to do to retail sales."

Merck & Co. continued to fall, dropping 31 cents to $27.58 after Friday's $253.4 million verdict against the company in the first of 4,200 suits claiming Merck knew of problems with its Vioxx painkiller long before it pulled the drug from the market.

Declining issues led advancers by more than 9 to 7 on the New York Stock Exchange, where consolidated volume was 1.72 billion shares, up from 1.66 billion Monday.