A combined study of possible atherogenic factors was carried out in 213 males subjected to clinical investigation including selective angiography of the heart's coronary arteries. Two sets of biochemical tests were used: the routine set including the measurement of the plasma lipid spectrum, and a more sophisticated procedure (93 cases) where plasma apoproteins A1 and B, and high-density lipoprotein phospholipid composition were assessed as well. A correlation of biochemical disorders to coronary atherosclerosis could be demonstrated in 68% of cases, using the first set, and in 98% with the second set. Abnormal apoprotein levels and high-density lipoprotein phospholipid composition were found to contribute significantly to lipoprotein atherogenesis even in cases of normolipidemia.