We observed the cholesterol metabolism of a colony of Wistar rats with a hereditary defect in vitamin C synthesizing ability (the ODS (osteogenic disorder-Shionogi) rats) in six kinds of experiments. Female ODS rats aged 36 days had a low HDL (high-density lipoprotein)-cholesterol level in serum as compared with age-matched control rats in spite of the absence of scorbutic symptoms. Female ODS rats aged 63 days which revealed severe scorbutic symptoms had a very low HDL-cholesterol level (mean value; 17 mg/dl). And male ODS rats, whose lives had been prolonged by supplementing with L-ascorbic acid, also had lower serum HDL-cholesterol and had increased total cholesterol in serum and liver when the acid supplement dose was relatively insufficient. On the other hand, we examined HDL2- and HDL3-cholesterol levels in serum to determine the mechanism of low HDL-cholesterol. As a result, we observed a low HDL2-cholesterol level in ODS rats but normal HDL3-cholesterol level. But the authors observed no decrease of LCAT (lecithin: cholesterol acyltransferase) activity in serum of ODS rats. These results could be due to disturbance of lipid metabolism in a vitamin C-deficient condition, that is to say, there might be abnormalities of the cholesterol excretion pathway of bile acid from liver, and maturity of the HDL-cholesterol particle due to other factors except that of LCAT activity.