This report deals with the foods eaten by Salvelinus pluvius which were fished in three streams, namely, the Higashi-zawa, Sawagurumi-zawa, and Ôtori-gawa, of which the former two were the inflows and the last is the outflow of LakeÔtoriike, Yamagata Prefecture. The results of analysis of the contents of twenty-nine stomachs showed that the majority of foods eaten were insects, both aquatic and terrestrial. The aquatic foods are composed chiefly of caddis worms and stonefly nymphs, and in particular the nymph ofScopura longa. The terrestrial foods are represented by ants, wasps, and beetles. The fishes (S. pluvius) of the Higashi-zawa and Sawagurumi-zawa took chiefly aquatic foods which made up 52.9-56.9 volume per cent. of foods eaten, while the fishes of the Ôtori-gawa ate chiefly terrestrial foods, 47 volume per cent. of foods eaten (Fig.1). The nematode parasite Spiroptera salvelina FUJITA was found in the stomachs. Its parasitic frequency is the highest in the fishes from the Otori-gawa and is the lowest in those from the Higashi-zawa.