An outbreak of gastrointestinal illness caused by norovirus occurred among attendees of a birthday party in Bloomington, Minnesota. Ten of the 49 guests became ill. Stool samples from five persons revealed the presence of Norovirus. The case-control study was unable to determine the contaminated food even after using many different models. The grocery store was inspected, but no violations were found. However, an employee noted that the produce warehouse manager did not always wear gloves, and let his family members do the same. The fruit platter served at the party was assembled in the warehouse.