Minnesota Department of Health received a report of gastrointestinal illness on August 16 from a group who had eaten at a company picnic in Melrose, Minnesota. A list of attendees was compiled and interviews conducted to assess further illnesses and determine the contaminated food. A total of 33 people met the case definition of illness, and stool samples from six were submitted for testing. Five of these tested positive for Norovirus. Statistical analysis of the food histories indicated consumption of potato salad was significantly associated with illness. The potato salad was prepared at a private home, but neither members of this household nor the people who plated the salad reported illness. The outbreak was likely due to contamination of the potato salad at the picnic.