This study was performed to investigate the effects of different fat diets on the serum lipid composition and on the morphology of liver tissue of the spontaneously hypertensive rats(SHR), Rats were fed for 17 weeks one of four fat diets, control(corn oil : beef tallow=1:1), beef tallow, grapeseed oil and soybean oil. Blood was withdrawn by heart puncture from each SHR, and used to determine the serum levels of total cholesterol, HDL-cholesterol, trigly ceride and phospholipid. No significant difference in body weight was observed in all diet groups. the total serum cholesterol was significantly lower in SHR fed grapeseed oil than that of other groups. The cholesterol lowering effect of grapeseed oil seemed to results from its high contents of phytosterol and linoleic acid. Also, serum HDL-cholesterol, triglyceride and phospholipid contents were low in all the groups. photochemical microscopic observations of the liver tissue revealed the congestion of sinosoid which is regarded as the characteristics of SHR, but no significant difference was observed among the groups.