An outbreak of norovirus in participants on rafting trips occurred between August 19 and September 12. A total of 16 river rafting companies made these trips. Thirteen (14%) of the ninety one trips were linked to three or more cases of gastroenteritis; these trips were sponsored by only 5 of the 16 companies. These five companies had purchased food from the same three suppliers. No other common factors were identified. A case control study revealed that eating deli meat while river rafting was associated with illness. All deli meat had been purchased from one processing plant and had been served on the affected rafting trips. The investigation found that a processing plant worker had sliced meat with bare hands one day after recovering from gastroenteritis; the plant worker's stool sample, collected one month after the meat had been processed, was negative for Norovirus. Over 90% of this batch of meat had been sold to the river rafting companies; the rest to a restaurant. On the rafting trips, the vacuum-packed meat was frozen, then thawed, and served uncooked. The restaurant had cooked the meat prior to serving; no illness was linked to the restaurant. The same strain of Norovirus (GII.14) was detected in two of five sealed frozen meat packages and in two of three stool specimens from case-patients who had rafted on three different trips.