Laboratory examinations on fecal specimens collected from 34 subjects who complained of diarrhea on an occasion of group checkup in January 1987 at Bacolod City, Negros Island, the Republic of the Philippines, revealed Vibrio furnissii in 2 of these cases (5.9%). Meanwhile, in June 1987, three siblings who had eaten a luncheon packed in a chip box, especially fishes and shellfishes such as sliced raw turbo, ark shell and tuna meat, deep fried prawns and mackerel sushi served at a Buddhist service for the death, developed diarrhea in a Osaka City. Bacteriological examination of fecal specimens from them demonstrated Vibrio furnissii. These three cases were diagnosed as food poisoning due to contamination with this pathogen. Diarrhea, gripes, nausea, vomiting and fever were the principal manifestations with which all these patients presented. The symptoms appeared 10-14 hours after the luncheon and diarrhea persisted for 12 to 30 hours. One patient had mixed infection with Vibrio parahaemolyticus and was eventually in a serious condition with dehydration. These three cases of food poisoning due to Vibrio furnissii infection are the first to be reported in Japan, to our knowledge. It is generally recognized that pathogenic strains of Vibrio furnissii and Vibrio parahaemolyticus cause infection in man chiefly by way of contaminated fishes and shellfishes, hence important as causative agents for food poisoning.