In 2006, approximately 870 people from 33 states, participated in the Biking Across Kansas (BAK), an annual recreational cycling event that started at the western Kansas-Colorado border and ended at the Kansas-Missouri border. An outbreak of nausea, vomiting, and diarrhea caused by norovirus occurred among participants. No single activity at the event was identified as a cause of this outbreak. The outbreak was propagated by person-to-person transmission. Several food items at Support and Gear (SAG) stops, lack of bathroom facilities, and self-serving by participants at Support and Gear stops contributed to the spread of this outbreak. Counties along the event route had no reported outbreaks that were linked to this event.