In this study covering more than 150,000 person-years from women younger than 55 years of age, 61 survived a first acute myocardial infarction (AMI). Of these, 59 were compared with a random sample from the same population regarding serum lipids and apolipoproteins (apo) A-I, A-II, B, and E, as well as several other cardiovascular risk factors. Mean values of serum cholesterol, triglycerides, apo B, and apo E were significantly higher and high density lipoprotein cholesterol and apo A-I were significantly lower among patients with infarction than among controls. Those who sustained and survived an AMI more often had a history of hypertension and of tobacco smoking than did the controls. Cigarette smoking, a history of hypertension, age, high serum triglycerides and apo E, as well as low levels of apo A-I, were independently and significantly associated with infarction. Sixty percent of the cases and 11% of the controls were distributed in the highest quartile of risk. A major contribution to the association with AMI was accounted for by the conventional risk factors, cigarette smoking and hypertension, as well as high serum triglycerides. In this group of relatively young women, high serum triglycerides were strongly associated with infarction, while levels of serum cholesterol were not.