The study investigated the serum lipid metabolism and enzyme activities of Korean teas for their preventative activity against chronic disease and obesity. Male Sprague-Dawley rats were raised for 8 weeks on four experimental diets: normal diet, hyperlipidemic diet, and hyperlipidemic diet to which green and black teas (2% each) were added. Various biological actions, including lipid metabolism and enzyme activities of the serum, were investigated. Diet-induced, hyperlipidemic rats fed with green and black teas, showed significant decrease in food efficiency ratio, triglyceride, total lipid, and phospholipid compared to control, i.e. the normal and diet-induced, hyperlipidemic rats. Total cholesterol, LDL-cholesterol, Al(atherogenic index), LHR, VLDL-cholesterol, ester-cholesterol, and free-cholesterol also showed a significant decrease. However, there was no significant difference between the tea-fed, diet-induced, hyperlipidemic dieted groups. HDL-cholesterol concentration was increased significantly in the tea-dieted and normal groups compared to the control. There was a little difference in lipase activity between the normal and control groups, although green and black tea-dieted experimental groups were both increased compared to the control. The contents of total lipid, triglycerides, and total cholesterol were decreased in the normal and experimental groups compared to the control. The GOT, GPT, ALP and LDH serum enzyme activities of the experimental groups were significantly reduced compared to those of the control groups.