Gastroenteritis caused by Cryptosporidium occurred among members of a group attending a dinner banquet at a Spokane, Washington restaurant on December 18. The ill (87% of the group) had diarrhea and/or abdominal cramping within 10 days of eating the meal. Several persons had persistent symptoms that lasted for one month or longer. The banquet buffet included 18 separate food and beverage items; seven of these items contained uncooked produce. No single food was associated with illness. Green onions were suspected, but the data were inadequate to confirm them as the vehicle of infection. Two of the food workers had Cryptosporidium in their stool. Food workers reportedly ate food items served at the banquet associated with the outbreak. The green onions had not been washed prior to delivery at the restaurant, and food workers indicated that they had not consistently washed the green onions prior to serving to the customers. Two other banquets had occurred at the restaurant on December 18 and 19; the menus were similar, but no illness was associated with these banquets.