By the method mentioned above, the increasing amounts of consumed KMnO_4 of several kinds of fishes, shell-fish and “Kamaboko” have been measured. The increasing curve of the amounts of KMnO_4-consumption was sharper than that of volatile basic nitrogen which is usually measured as an index of spoilage. The amount of KMnO_4-consumption at an early stage of spoilage was different according to the kinds of fishes, at 20~30cc. Satisfactory result was obtained with shark fish, the freshness of which can not be determined by measuring volatile basic nitrogen, though its increasing curve was not so sharp as those of other fishes.