To elucidate the role of apolipoproteins in the evolution of hyperlipidemia in patients with myocardial infarction, VLDL apolipoprotein C and E isoforms were studied. VLDL-remnant and LDL-cholesterol ...levels were significantly higher during acute phase in myocardial infarction than in controls. On isoelectric focusing patterns of apo VLDL, there was an increased content of apo C-III2 and reduced content of apo C-III0 in patients with myocardial infarction. Apo E2/E3 ratio in VLDL were higher in patients with myocardial infarction than in controls. There was a significant positive correlation between apo E2/E3 ratio and VLDL-TC/TG. The incidence of variant pattern with apo E4 isoprotein was significantly higher in patients with myocardial infarction than in controls. Therefore it is suggested that the existence of apo E4 or the relative decrease of apo E3 or abnormal composition of apo C subspecies may modify the lipoprotein metabolism and contribute the development of atherosclerosis in patients with myocardial infarction.