From November 16 through December 21, 1994, a total of 20 laboratory-confirmed cases of diarrhea caused by Escherichia coli O157:H7 were reported to the Seattle-King County Department of Public Health (SKCDPH). In comparison, three cases were reported during October 1994. Epidemiologic investigation linked E. coli O157:H7 infection with consumption of a commercial dry-cured salami product distributed in several western states. Three additional cases subsequently were identified in northern California. This report summarizes preliminary findings from the outbreak investigation.