Coronary angiography was performed 3 to 6 months after myocardial infarction in 107 males below the age of 45 (mean age 39.7±3.9, range 23–44 years). The coronary angiograms were allocated to various groups according to the presence or absence of obvious atheromatous changes. Metabolic evaluation included determination of cholesterol and triglyceride concentrations in the major serum lipoproteins. Marked elevation of low density lipoprotein (LDL) cholesterol concentration was found in patients with angiographic evidence of atheromatosis, in contrast to patients with normal coronary angiograms or with single occlusion and no other abnormalities. Thus, there was a correlation between angiographic appearance of the coronary arteries and disturbances of LDL metabolism. It is proposed that coronary angiography may distinguish between atheromatous and non-atheromatous pathogenesis of myocardial infarction at young age.