AbstractMany reports have described the amounts of atherosclerotic plaque in victims of sudden coronary death, defining the number of coronary arteries narrowed at some point > 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 lumnial 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 = <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 = <0.001) and a lower mean percent of segments narrowed minimally in those with a left ventricular scar (13% vs. 26%, p= <0.001). Those patients with higher heart weights (>450 grams) compared with those with lower heart weights had a higher mean percent of segments severely narrowed (23% vs. 19%, p = <0.01) and a lower percent of minimally narrowed segments (24% vs. 29%, p = <0.005) in the large heart group. Patients in each decade had similar mean percents of severely narrowed segments. Thirteen patients had a coronary artery thrombus, and in each the thrombus occurred at a site narrowed >50% by plaque. Seven patients had disrupted fibrocellular caps at the site of thrombus, and the role of “plaque fissuring” is examined.