A holiday banquet catered by a local restaurant was followed by an outbreak of gastroenteritis. Of the 93 people who attended this party, 41 reported illness, and 39 fit the case definition established by the health departments. A cohort study was performed by asking all the attendees what they had eaten at the party. This did not indicate any particular food item associated with illness. However, the health department workers found in the course of their interviews that many of the cases appeared to be secondary cases due to person-to-person contact, and that two children at the event had diarrhea during the party. They suspected Norovirus, and this was confirmed with three stool samples. They were unable to find a particular food item, and suspected contamination of the food at the party.