Among one year cherry salmon Oncorhynchus masou reared in freshwater, we found that non-polar lipid contents in the whole body, dorsal muscle, and liver of the smolt were lower than those of the parr. During March through May, nonesterified fatty acid levels in the plasma of the smolt were higher than those of the parr, but the neutral fat levels in the smolt were lower. Later, growth response and smolt production in 1 yeaz cherry salmon with mean weight of about 16g were studied by feeding the following four diets for 120 days: HPHL, high protein (41%)-high lipid(16%);HPLL, high protein(41%)-low lipid(4%);LPHL, low protein(24%)-high lipid (14%); LPLL, low protein (24%)-low lipid (2%). The growth response to these dietary treatments was as follows: HPHL (final mean body weight, 44.41g)_??_HPLL (36.47g)_??_LPHL (24.04g)_??_LPLL (28.02g). Only in the HP diets, both growth rate and feed efficiency were clearly improved by addition of lipid. In all treatment groups, the growth, feed efficiency, and feed consumption rate were accelerated with the onset of smoltification. Percentages of smolt pro-duced were 74.5%, 47.3%, 29.1%, and 16.4%for HPHL, HPLL, LPHL, and LPLL, respectively. Thus, supplementation of lipid to diet seems to be one of the valuable method to promote smolt production.