Men (1306) who survived a first myocardial infarction (Ml) were studied. The mean follow-up time was 6.5 yr, and at the end of the follow-up period survival status was known for all patients. By the time of the Ml the prevalence of diabetes was 5.6%. Patients with and without diabetes were compared. There were no differences in the estimated primary or secondary risk. The cumulative survival rate 1, 2, and 5 yr after the Ml was 82, 78, and 58% among the diabetic subjects compared with 94, 92, and 82% among the nondiabetic subjects (P < 0.001). The difference remained even after allowance for age and estimated secondary risk in a multivariate regression analysis. There were no differences in mortality rates among patients with type I diabetes compared with type II diabetes, nor among patients treated with diet alone, sulfonylurea, or insulin, but the numbers were small. The cumulative rate of reinfarctions after 1, 2, and 5 yr was 18, 28, and 46% in diabetic subjects and 12,17, and 27% in nondiabetic subjects (P = 0.004). A history of diabetes was an independent secondary risk factor among male survivors of a first Ml with respect to deaths and reinfarctions.