This report compares quantitative measures of atherosclerosis in aortas and coronaries from autopsies of deceased men from Mexico City collected during 1960 to 1964 and 1986 to 1987. The comparison of lesions in two different time periods provides an opportunity for determining whether the extent of atherosclerosis has changed over time in Mexico City. Three pathologists independently evaluated the extent of fatty streaks (FS), fibrous plaques (FP), calcified plaques (CA), and complicated lesions (CO) in 165 aortas and 120 sets of coronary arteries collected during 1986 to 1987 for comparison with similar gradings of 128 aortas and coronary arteries from the International Atherosclerosis Project in 1960 to 1964. Neither FS nor more advanced lesions differed significantly in either the descending thoracic or abdominal aorta between the two collection periods. In contrast, there were more extensive FP and raised atherosclerotic lesions (RL = FP + CA + CO) in the coronary artery segments evaluated in the younger age groups in 1986 to 1987 versus 1960 to 1964. Additional analyses, based on 75 pairs of aortas and 32 pairs of coronary arteries from age-matched cases, all regraded by the team of pathologists after blind coding, showed more FS in both aortic segments and more extensive involvement with RL in the three main branches of the coronary arteries in the more recent study. An overview of our findings suggests that atherosclerosis, particularly in the coronary arteries, is increasing in Mexico City. This hypothesis merits careful testing in parallel with consideration of possible changes in the risk factors that could be responsible for changes in extent of lesions.