SummaryWe 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; 17mg/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 HDLz and HDL3-cholesterol levels in serum to determine the mechanism of low HDL-cholesterol. As a result, we observed a low HDLz-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 .