We compared age- and race-specific data from two autopsy studies conducted 10 years apart on 25- to 44-year-old New Orleans men. The per cent of coronary intimal surface having raised atherosclerotic lesions was substantially less for white men in the later study. For black men of the same age group, however, the mean extent of raised atherosclerotic lesions in the coronary arteries changed only slightly. Fatty streaks were less extensive in both races in the second study period. Thus, the total surface involvement with coronary atherosclerosis in both black and white men was less in the second study. This apparent reduction in coronary atherosclerosis is consistent with recent evidence of diminishing coronary heart disease mortality in the United States. These findings suggest that surveillance of the extent of atherosclerotic lesions measured at autopsy may be an effective indicator of secular trends in coronary heart disease.