In an attempt to examine whether the VLDL secreted by diabetic rats may be different from that by normal rats, plasma obtained after Triton WR-1339 treatment was analyzed. After Triton treatment, a marked increase in plasma triglyceride levels with lesser increases in cholesterol and phospholipids was observed in both diabetic and control rats. The degree of such increases was almost equal between two groups of rats. The large increases in plasma lipid levels presumably reflect the increase in plasma VLDL fraction. The lipid composition of VLDL of diabetic rats was very similar to that of normal controls. The LDL fraction of diabetic rats was low in its contents of both cholesterol and phospholipids compared with that of normal controls. The composition of IDL and HDL in diabetic rats was similar to that of controls. From these data, we suggest that the VLDL of diabetic rats secreted under basal fasting condition is not different in its lipid composition as well as in amounts from that of controls.