Many reports have described the amounts of atherosclerotic plaque in victims of sudden coronary death, defining the number of coronary arteries narrowed at some point greater than 75% in cross-sectional area (XSA). In order to quantitate more precisely the amount and distribution of plaque, 70 victims of sudden coronary death aged 22-81 years (mean 50) were studied. The four major epicardial coronary arteries (left main, left anterior descending, left circumflex, and right) from each of 70 victims were cut into 5-mm segments (average 50 per patient) and a histologic section prepared from each segment. The amount of luminal narrowing by plaque was categorized into five groups (0-25%, 26-50%, 51-75%, 76-95%, 96-100%). Of 3,484 five-mm segments, 950 (27%) were narrowed 76-100% in XSA. Comparison of 31 previously symptomatic victims (angina pectoris and/or myocardial infarction) to 39 victims who had been asymptomatic disclosed a higher mean percent of severely narrowed segments (30% vs. 25%, p = less than 0.005) and a lower mean percent of minimally narrowed segments in the symptomatic group. Comparison of the 31 patients with a healed myocardial infarction at necropsy with 39 patients with no left ventricular scar disclosed a higher mean percent of segments severely narrowed (33% vs. 24%, p = less than 0.001) and a lower mean percent of segments narrowed minimally in those with a left ventricular scar (13% vs. 26%, p = less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)