1. 1. During the starvation of the eel (200 days), the rainbow trout (62 days) and the Japanese dace (75 days), white muscle free l-histidine decreased rapidly in every species, while carnosine and anserine levels in the eel and trout, respectively, exhibited relatively smaller percentage changes. 2. 2. Accompanying sea-water acclimation, l-histidine in skeletal muscle of the ell and trout increased 2- and 5-fold, respectively, but in dace muscle no significant chenge occured. The concentration of carnosine in the eel and anserine in the trout remained almost at constant levels even in sea-water.