The effects of fruiting body of Cordyceps militaris on the growth, the food intake, the food efficiency ratio, the lipid metabolism, the serum protein level ad enzyme activity in male rats were studied. Sprague-Dawley rats were fed four types of diets for five weeks, respectiely: a control diet, a control diet supplemented with 2%, 3% or 4% fruiting body of Cordyceps militaris(CF) powder. In rats fed 2% or 3% CF diets the body weight gain, the food intake, the concentratons of hepatic triglyceride and serum LDL-cholesterol, the atherogenic index, and the total lipid, total cholesterol, triglyceride and phospholipid in serum were similar to those in rats fed the control diet. Whereas, in 4% CF diet these were significantly decrased. But the all CF diets feeding could not decrease the food efficiency ratio, the weights of liver, pancreas, spleen, kidney and heart, and the concentration of serum HDL-cholesterol. Also, it was shown that the concentrations of glucose, total protein, albumin, urea and creatinine, and the GOT, GPT, LDH, ${gamma}$-GTP and ALP activities were the same levels in serum of rats of fed all the experimental diets.