The purpose of this study is to investigate the effect of taurine on the plasma cholesterol concentration in genetic type 2 diabetic rats fed cholesterol-free or high-cholesterol diets. Diabetic rats (GK male rats) and normal rats (Wistar male rats) were fed either a cholesterol-free or cholesterol-enriched (1% cholesterol + 0.25% sodium cholate) diet supplemented with or without 3% taurine for 21 or 14 d. Compared to the normal rats, diabetic rats showed a high glucose concentration in their blood and plasma, but it was not affected by taurine feeding. The plasma insulin concentration was higher in the diabetic rats than in the normal rats. At the start of the experiment, the plasma cholesterol concentration was significantly higher in the diabetic rats than in the normal rats. Taurine did not affect the plasma cholesterol level in rats fed the cholesterol-free diet. However, taurine feeding significantly increased the plasma HDL-cholesterol concentration in the diabetic rats fed the cholesterol-free diet. In both the diabetic and normal rats fed the cholesterol diet, the plasma cholesterol concentration was significantly lower in rats fed the diet supplemented with taurine than in the rats fed the control diet. It was concluded that taurine has a hypocholesterolemic effect in both diabetic and normal rats fed diets containing cholesterol. Moreover, these results suggest that taurine seems to affect the HDL-cholesterol metabolism in diabetic rats fed a cholesterol-free diet.