The sera of coronary patients with angiographically-documented stenosis of 1 to 3 coronary arteries caused a two-to-fivefold accumulation of intracellular cholesterol in intact human aortic intimal cell culture. This property, qualified as "atherogenic", was exhibited by the sera of 90% of the coronary patients examined (97 males and females, aged 29 to 55 years). Only 20% of normal subjects revealed atherogenic properties in cell cultures. The capacity of the sera to accumulate intracellular cholesterol was unrelated to the levels of total cholesterol, high density lipoprotein cholesterol, apo-B or apo-AI, taken separately, but showed a weak correlation to the apo-B/apo-AI ratio. The sera of coronary patients caused lipid accumulation in human aortic medial smooth-muscle cells and blood mononuclear cells, in human and mouse peritoneal macrophages, but never in human aortic or umbilical vein endothelial cells, nor human embryo fibroblasts.