In the investigations on the mode of outbreak, general symptoms and causative bacteria concerning a food poisoning incident that broke out on August 14, 1958 in a factory in Hiroshima prefecture, the author has been able to clarify the following points. 1. Of 269 persons partaking the same meals, 88 persons were attacked by food poisoning, namely, 32.7 per cent of the total; and of them 38.6 per cent developed the symptoms making them unable to work. A higher percentage was in female, but relatively severer cases were among males. As for the age range in the age ranging 20-30 years and in those above 50 years the percentage was low, but the symptoms in those above 50 years were relatively severe. 2. The latent period appeared to be 12-24 hours in most of them. 3. As for the symptoms the patients showed an acute gastroenteritic picture such as diarrhea, abdominal pain, nausea and vomiting, accompanied by fever and headache. 4. The majority of them recovered on the second or on the third day afterwards. 5. The food in question was assumed to be the ones served on August 13th, the day before the outbreak of poisoning. From the findings of excreta culture in 5 patients Salmonella were detected, and by the antigen analysis it was determined as Salmonella dublin.