Five groups of people, who ate at a Rochester, Minnesota, restaurant, between March 3 and March 7, reported gastrointestinal illnesses to the Minnesota Department of Health. The groups had eaten at separate events that had been catered by the restaurant. People who had eaten the meals were interviewed to find out what they had eaten and if they had become ill. The analysis of the data showed that consumption of lettuce based salads was associated with illness. Stool samples confirmed the illness was due to Norovirus, which is often found on ready-to-eat items such as lettuce. The catering business was inspected; food workers reported family members with illnesses. Obstructed handwashing sinks were observed, and the catering and salad stations did not have conveniently located handwashing sinks. Contamination of the lettuce was likely due to an infected food worker handling the lettuce with bare hands.