Little is known about the direct relationship between serum cholesterol and the extent of coronary atherosclerosis in human populations even though the association of serum cholesterol levels with risk of developing coronary heart disease (CHD) is well documented. The results of this study of men 25-44 years of age, residents of Orleans Parish, Louisiana, show a significant relationship between post mortem serum cholesterol levels and extent of more advanced lesions (raised lesions) in the coronary arteries in 110 autopsied white men, but not in the cases of 221 autopsied black men. When disease categories comprising CHD cases and non-CHD cases (basal group) were evaluated, the racial difference in the cholesterol-lesion associations persisted. The reason for the racial difference in the observed cholesterol-lesion association is not clear. Additional research, where younger age groups are included, and considering earlier lesions and other risk factors in different environments may help in clearing this question.