The present studies were designed to observe the effects of both dietary fat levels and P/S ratio on lipid components in plasma and tissues of young rats when cholesterol was supplemented at 1%(w/w) to four dietary groups providing total fat as 10%( LF ) or 45% ( HF ) of calories and P/S ratio as 0.2 or 4.0, Low Fat-0.2 : Low Fat-4.0 : High Fat-0.2 : High Fat-4.0. Plasma total cholesterol was increased almost to the same level in all dietary groups after the cholesterol supplement but the value of HF -0.2 was slightly higher than that of LF -0.2. Plasma TG was also increased in all dietary groups when cholesterol was supplemented but was more significantly increased in LF group than in HF group. HDL-cholesterol was slightly increased by cholesterol supplement but there was no effect by the total dietary fat level of previous diet. However, plasma HDL-cholesterol, total cholesterol and TG levels were slightly reduced in high fat diet of P/S 4.0. Total cholesterol per g -liver was higher in HF group than in LF group before and after cholesterol supplement even though it was increased more in LF group with cholesterol addition. Liver cholesterol was also higher in rats fed diets of P/S 4.0 at high fat level before and after cholesterol supplement. In contrast, total cholesterol per g-muscle was reduced by cholesterol supplement in all groups and it was significantly higher in LF than in HF. There was no significant effect in liver TG by total fat level and P/S ratio when cholesterol was supplemented. Muscle TG was lowered in all groups by cholesterol supplement but no effect by total fat level and P/S ratio.