To ascertain the frequency of defined hyperlipoproteinemia and to investigate the relation between lipoprotein fractions and coronary heart disease, we measured serum lipoprotein cholesterol levels in a population-based sample of Hawaii Japanese men 50 to 72 years old. Type II hyperlipoproteinemia was present in 3 per cent of 1859 men, and Type IV in 26 per cent. Relative risks for coronary heart disease, based on 264 prevalence cases, were found to be 1.8, 1.8 and 0.46, between the upper and lower quartiles of total, beta, and alpha cholesterol, respectively. We found no significant relation between triglyceride and coronary heart disease. The inverse relation of alpha cholesterol of prevalence of coronary heart disease was independent of beta cholesterol, obesity, and other factors. The data suggest the need for further evaluation of the protective effect of the alpha lipoprotein fraction on the development of coronary heart disease.