Gender differences in the effects of gonadectomy and high cholesterol diet on body weight and body cholesterol were investigated by using Sprague Dawley rats. Body weight, plasma and liver levels of cholesterol and triglyceride and platelet aggregation were examined in ovariectomized(OVX) or orchidectomized(ODX) rats with their intacts after feeding diet with or without 0.5% cholesterol. Body weight was significantly increased(p < 0.01) in OVX rats and significantly decreased(p < 0.01) in ODX rats compared to their respective intact rats, and cholesterol diet significantly(p < 0.05) decreased body weight in gonadectomized rats. Liver lobes from rats fed cholesterol diet were opaque and larger than those from rats find control dict, resulting in a significant increase(p < 0.01) in LW/BW ratio. Plasma and liver levels of total cholesterol were significantly increased (p < 0.01) in female rats regardless ovariectomy when find 0.5% cholesterol diet, but those levels in male rats were increased only when they were orchidectomized(p < 0.0l). Plasma HDL-cholesterol was significantly decreased(p < 0.05) in both sexes when find cholesterol diet. HDL-cholesterol were higher in female than male rats regardless treatments(p < 0.05). Liver triglyceride was significantly increased(p < 0.05) in both sexes when find cholesterol dict. Plasma level of triglyceride was not different among groups except significant decrease(p < 0.05) in cholesterol find ODX rats. Maximum platelet aggregation in female rats was significantly lower(p < 0.05) than male, but ovariectomy and cholesterol diet caused an increase te the level of male rats. Microscopic examination showed cholesterol diet caused a lipid accumulation in liver. Results indicate that intact female rats have higher response to hypercholestcrolemic diet than intact male rats and orchidectomy causes male rats more responsive to hypercholesterolemic diet. However, ovariectomy causes an increase female food efficiency ratio to the level of male rats, significantly increasing body weight.