The risk of nonfatal acute myocardial infarction (AMI) has been studied in relation to diabetes and other risk factors, combining data from three Italian case-control studies including 1,737 cases with nonfatal AMI and 2,317 controls in hospital for acute diseases unrelated to AMI risk factors. The multivariate odds ratio (OR) of AMI for diabetes was 2.3 (95% confidence interval, 1.8-2.9); the association with AMI risk was apparently stronger in patients diagnosed with diabetes when aged <40 years (OR 2.9), and in women (OR 4.4). When the combined effect of diabetes and other known risk factors on the risk of AMI was considered, compared to nondiabetic subjects with each factor at the lowest risk level, the OR for diabetic subjects was 4.7 in smokers, 2.8 in heavy coffee drinkers, 2.7 in those with higher body mass index, 3.4 in patients with high cholesterol levels, 3.3, 4.3, and 2.7 for diabetic subjects with history of hyperlipidemia, hypertension, and obesity, respectively, and 4.3 for those with a family history of AMI in first degree relatives. The association of each risk factor was much stronger in diabetic women. Preventive measures to reduce the prevalence of each additional risk factors in diabetic subjects could led to a substantial reduction of risk of AMI.