The effects of the fruiting body of Agaricus blazei Murill on the weight gains, food intakes, food efficiency ratios, serum and hepatic lipids concentrations were investigated in male rats. Sprague-Dawley rats, 21 weeks old, were given four different types of diets for a succeeding period of 10 weeks: either a normal diet (5% corn oil), a high fat diet (high fat; 20% lard), a 3% or 5% Agaricus diet (high fat diet+3% or 5% Agaricus powder). The body weight gains and food efficiency ratios of the rats fed 5% Agaricus diet were significantly lower than those of the rats fed high fat diet. The hepatic and kidney weights of the rats fed Agaricus diets were similar to those of the rats fed high fat diet. The epididymal fat pad weights of the rats fed 3% or 5% Agaricus diets were significantly lower than those of the rats fed high fat diet. The concentrations of hepatic and serum triglyceride in the rats fed 5% Agaricus diet were significantly lower than those in the rats fed high fat diet. But the hepatic total cholesterol of rats fed the 3% or 5% Agaricus diets were similar to those of rats fed the high fat diet. The concentrations of serum total cholesterol, LDL-cholesterol and atherogenic index in rats fed the 3% or 5% Agaricus diets were significantly decreased compared with those of rats fed the high fat diet. The HDL-cholesterol/total- cholesterol ratios of the rat fed 3% or 5% Agaricus diet were significantly increased compared with those of rats fed the high fat diet. There were no differences in serum concentrations of HDL-cholesterol and phospholipid among the experimental groups. These results showed that the 5% Agaricus diet feeding decreased the total cholesterol, the triglyceride, the LDL-cholesterol and the atherogenic index, and increased the HDL-cholesterol/total-cholesterol ratio in serum of rats.