An outbreak of E. coli O157:H7 infections occurred among patrons of Oregon-based, Wendy's Restaurants. Several cases were at first linked to a Wendy's Restaurant in Salem, Oregon. A case was subsequently linked to the Wendy's Restaurant in Tualatin. The health department investigation revealed that cross contamination from contaminated ground beef was likely to have been the outbreak source. Although some cases had eaten ground beef, others had not. Lettuce was prepared in sinks that was used to rinse meat juices from pans. Dry, bloodied towels were used for hand wiping. Poor handwashing was observed. The ground beef for both restaurants was purchased from the same supplier. The E. coli O157:H7 isolated from the Tualatin case matched the strain isolated from the Salem cases.