The incidence of coronary heart disease is supposedly influenced by dietary fish-oil intake. The purpose of this study was to investigate the possible beneficial effect of fish consumption on coronary atherosclerosis. Adipose-tissue biopsies and segments of coronary arteries were sampled from 40 consecutive autopsies. Degree of coronary artery disease was estimated quantitatively by morphometry, and the fatty acid composition of adipose tissue was analyzed with gas-liquid chromatography. The group with the highest degree (68-92% stenosis, n = 13) of coronary artery disease had lower concentrations of docosahexaenoic acid in adipose tissue than did the group with the lowest degree (23-53% stenosis, n = 13) of coronary artery disease (P less than 0.05). Multiple-regression analysis showed that the degree of coronary artery disease was dependent on docosahexaenoic acid in adipose tissue (P less than 0.01) and body weight (P less than 0.05). The study supports the hypothesis that fish consumption is associated with a reduced risk of coronary heart disease.