Proximate composition and nitrogenous extractive components in several tissues of four fishes, yellowtail, Japanese flounder, Spanish mackerel and common carp, were analyzed and compared. No significant differences were observed in the amounts of protein and ash between fishes or tissues. Levels of lipids were relatively high in the liver of Spanish mackerel and Japanese flounder and also in the dark muscle of yellowtail, compared with those in the white muscle. IMP was in higher levels in the white muscle of all fishes, while GMP was comparatively abundant in some visceral tissues. The white muscle of yellowtail and Spanish mackerel was rich in histidine; the other tissues contained higher levels of taurine. Among the nitrogenous extractive components, larger amounts of unidentified constituents were found in the viscera than in the muscle tissues. Strength of umami taste calculated from the amounts of IMP, GMP and glutamic acid (Glu) varied from tissue to tissue. There was a tendency that the strength in white muscle depends on levels of the nucleotides but that in visceral tissues on that of Glu. It was suggested that the umami strength is not always stronger in the muscle tissue than that in the visceral tissues.