Oil fell to the lowest level since March Monday as traders worried about signs of weak demand and increasing supplies.
Chevron and Exxon Mobil were among the biggest decliners in the Dow Jones industrial average.
Investors were also watching company earnings. Tyson Foods slumped 10 percent after cutting its outlook for the year.
The Dow lost 91 points, or 0.5 percent, to 17,598.
The Standard & Poor's 500 index fell five points, or 0.3 percent, to 2,098.
The Nasdaq composite gave up 12 points, or 0.3 percent, to 5,115.