Lipid and apoprotein constituents of plasma lipoproteins were determined in survivors of myocardial infarction in relation to a control population. Compared to controls, the patients had significantly higher concentrations of total triglycerides, VLDL + LDL - cholesterol and apo-B, but lower concentrations of HLD-cholesterol, HDL2-cholesterol, HDL3-cholesterol, apo A-I and A-II. Survivors with normal lipaemia also had perturbations in HDL and subfractions (HDL2 and HDL3). In addition, the patients exhibited a significant decrease in HDL-cholesterol to VLDL + LDL-cholesterol ratio and in apo A-I to apo-B ratio. These results demonstrate the importance of determining all lipoproteins in future biological studies to evaluate more precisely the relationship between these compounds and atherosclerosis.