The effects of liquid culture of Agaricus blazei Murill on the weight gains, serum and hepatic lipid concentrations were studied in male rats. Sprague-Dawley rats (7 weeks old) were given four different types of diets for 6 weeks, respectively: a normal diet group, a high fat control diet group (normal diet+15% lard +0.5% cholesterol), a 30% or 40% A. blazei diet groups (high fat control diet+30% or 40% A. blazei in water) according to the levels of A. blazei supplementation. The body weight gains, food intake, food efficiency ratios, and the liver, kidney, and epididymal fat pad weights of the rats fed 30% or 40% A. blazei diets were similar to those of the rats fed high fat control diet. The concentrations of serum total cholesterol, LDL-cholesterol and atherogenic index in rats fed the 30% or 40% A. blazei diets were significantly decreased compared with those of rats fed the high fat control diet. The HDL-cholesterol/total-cholesterol ratios of the rats fed 30% or 40% A. blazei diet were significantly increased compared with those of rats fed the high fat control diet. The fecal excretion of total lipid . in the rats fed 40% A. blazei diet was significantly increased compared with those of rats fed the high fat control diet. The concentrations of serum total lipid in the rats fed 40% A. blazei diet was significantly lower than that in the rats fed high fat control diet. But the concentrations of serum HDL-cholesterol, hepatic total cholesterol and triglyceride of rats fed the 30 or 40% A. blazei diets were similar to those of rats fed the high fat control diet. These results showed that the 30 or 40% A. blazei diets feeding decreased the total cholesterol, LDL-cholesterol and atherogenic index, and increased the HDL-cholesterol/total-cholesterol ratio in serum of rats.