Discussing market operations, he said, "They seem to be working well, normally."
In what might have been a reference to Greenspan, Bernanke said there did not appear to be just one cause for Tuesday's sell-off.
The possible causes suggested by analysts ranged from a record drop in China's Shanghai index, a surprisingly weak U.S. manufacturing report and weekend comments by Greenspan that raised the possibility of a U.S. recession by year's end.