The atherosclerotic lesions from 4 major epicardial coronary arteries (left main, left anterior descending, left circumflex and right coronary arteries) of 23 nonagenarians patients were compared with that from 23 patients aged 60?9. The arteries were cut into transversely 5 mm long segments and were examined by microscope. The inside circumferences of the lumen were measured by computerized morphometric analysis. The results showed that the numbers of atherosclerotic plaques, percentages of narrowing of the coronary arterial lumen and circumferences of the arterial lumen in both groups were similar. But there were much more fibrous and resting (silent) or regressive plaques in the group aged 90-99 years as well as less lipid and active or progressive plaques than those in the group of 60-69 years. The above morphological findings may be correlated with the fact that there was a similar incidence of coronary heart disease but a less risk of acute myocardial infarction in patients aged 90?9 years than th The atherosclerotic lesions from 4 major epicardial coronary arteries (left main, left anterior descending, left circumflex and right coronary arteries) of 23 nonagenarians patients were compared with that from 23 patients aged 60-9. The arteries were cut into transversely 5 mm long segments The inside diameter of the lumen were measured by computerized morphometric analysis. The results showed that the numbers of atherosclerotic plaques, percentages of narrowing of the coronary arterial lumen and circumferences of the arterial lumen in both groups were similar. But there were much more fibrous and resting (silent) or regressive plaques in the group aged 90-99 years as well as less lipid and active or progressive plaques than those in the group of 60-69 years. The above morphological findings may be correlated with the fact that there was was similar incidence of coronary heart disease but a less risk of acute myocardial infarction in patients aged 90? 9 years than th