The Dow Jones industrial average was down 109.43 points, or 1. 07 percent, to 10,120.53. The Standard & Poor's 500 index fell 13. 89 points, or 1.28 percent, to 1,069.59 and the Nasdaq was down 35. 16 points, or 1.58 percent, to 2,187.33.
A drive for safe assets drove the dollar and yen higher Wednesday after Bernanke's speech. In late trading in New York, the euro slid to 1.2745 dollars from 1.2895 dollars late Tuesday.
Oil prices retreated Wednesday after the U.S. said crude supplies grew despite more demand for most types of fuel.
Comments from Bernanke about the fragile economy also pushed prices down.
Light, sweet crude for September delivery fell 1.02 dollars to settle at 76.56 dollars a barrel on the New York Mercantile Exchange.
In London, Brent crude fell 85 cents to settle at 75.37 dollars per barrel on the ICE futures exchange.