NAKAZAWA, K. and MURATA, K. Epidemiological Study of Serum High Density Lipoprotein Cholesterol with Respect to Risk Factors against Ischemic Heart Disease and Atherosclerosis. Tohoku J. exp. Med., 1981, 133 (2), 197-204-The aim of the present study was to elucidate the change of high density lipoprotein cholesterol (HDL-CHO) in healthy individuals of 111 males and 162 females in relation to risk factors against ischemic heart disease and atherosclerosis. A formula, (total cholesterol-HDL•CHO)/total cholesterol, was used as a risk factor index (RFI). The following data were obtained concerning serum HDL• CHO, total cholesterol and triglyceride, and other risk factors. A significant decrease in HDL•CHO was related to the RFI. With the increase of RFI, significant increases were found to various extents in serum triglyceride, total cholesterol, obesity index, blood sugar level, serum uric acid and the number of erythrocytes. The significant relations of these risk factors to RFI were discussed.