Two groups reported gastrointestinal illness due to Norovirus, on October 4. This prompted an investigation of a Plymouth, Minnesota, restaurant. Analysis of the second group's food history showed significant association between the consumption of the house salad and illness. The ill person from the first group refused any further inquiry after stating they had eaten chicken wings and vegetables. Employees were interviewed; the employee who had prepared the salads reported having illness three days before the groups ate at the restaurant. Food worker contamination of ready-to-eat foods was determined to be the cause of this outbreak.