During the period from 1952 to September 1955 there occurred in Niigata, Yamagata, and Nagano Prefectures, Japan, a series of intoxications from squid and octopus, involving 758 known outbreaks and a total of 2,874 persons. From June to September 1955 there were a minimum of 108 outbreaks, involving 2,159 persons in the Niigata Prefecture, Miyaka, Mikura, and Hachijo Islands, caused by scombroid and carangid fishes. The actual number of persons involved is believed to be considerably greater than is indicated by the preceding figures. The morbidity rate for the cephalopod intoxications was 27.1 per cent, and the fish intoxications 24.6 per cent. The mortality rate was found to be 0.77 per cent in given series of fish poisonings, and 0.84 per cent for the cephalopods. All of the intoxications occurred during the months of June through September. The symptomatology was that of a gastrointestinal upset. Neurological symptoms were largely absent, and the patients generally recovered within a period of 48 hours. Bacteriological tests failed to show evidence of any of the ordinary types of bacteria known to cause food poisonings. The etiology of these outbreaks is still unknown, but epidemiological studies are continuing.