This study investigated the effects of mulberry leaf extract on lipid metabolism in rats fed a high cholesterol diet. Sprague-Dawley male rats weighing $100{pm}10g$ were randomly assigned either to one of two normal diet groups, with (NE group) or without (N group) mulberry extract, or one of four high cholesterol groups containing 1% cholesterol and various levels of dietary mulberry leaf extract. The rats fed high cholesterol diets were subdivided into 4 groups according to level of mulberry extract; Mulberry extract free group (HC group), 0.8% mulberry leaf extract group (HCL group), 1.6% mulberry leaf extract (HCM group) and 3.2% mulberry leaf extract (HCH group). The rats were fed their respective diets ad libitum for 4 weeks. The levels of serum triglyceride, total cholesterol and LDL-cholesterol of the HC group were higher than mulberry leaf extract supplemented groups. In contrast, the levels of serum HDL-cholesterol in groups supplemented with mulberry leaf extract were significantly lower than that of HC group. Hepatic total lipids, triglycerides, and cholesterol were significantly higher in the high cholesterol groups compared to those of the normal group, but were lower in the HCL, HCM and HCH groups than in the HC group. HMG-CoA reductase activity was significantly decreased in the HC and HCL groups compared to the normal and NE groups. However, the activities in the HCM and HCH group were similar to that of the normal group. The activity of acyl-CoA-cholesterol acyl transferase (ACAT) was increased in high cholesterol groups compared to the normal group. However, the activity was lower for all of the high cholesterol groups fed mulberry leaf extracts, and was lowest for the highest supplemented group (HCH), with no significantly difference from the normal group. In conclusion, the reduction in serum and hepatic lipid composition by mulberry leaf extract may be due to its modulation of HMG-CoA reductase and ACAT activities.