Plasma cholesterol (CH), triglyceride (TG) and high density lipoprotein cholesterol (HDL-C) were measured in 92 consecutive Japanese male subjects undergoing diagnostic coronary cineangiography. Sixty-nine of them were classified as having coronary artery disease (CAD), the remaining 23 subjects were classified as having normal coronary arteries (NCA). The CAD group had significantly lower HDL-C and higher TG levels than the NCA group. However, there was no significant difference in plasma CH between the two groups. First-degree relatives of the CAD patients were also investigated. The male blood relatives of the CAD patients also had significantly lower HDL-C and higher TG levels than the non-blood male relatives and healthy control males. The female blood relatives, however, showed no significant differences from the non-blood female relatives and the healthy control females in plasma CH, TG and HDL-C levels. These results suggest that low HDL-C and hypertriglyceridemia are the prevalent coronary risk factors, rather than hypercholesterolemia, in a population with a low fat intake such as the Japanese, and that these lipid abnormalities are related to sex and genetic factors.