The aim of this study was to assess the preventive potential of major lifestyle risk factors for acute myocardial infarction (AMI) in middle-aged men. Among 10,981 men in the Heidelberg cohort of the European Prospective Investigation into Cancer and Nutrition, aged 40.2-65.8 years when recruited, 378 developed first-ever AMI during a median follow-up period of 11.4 years. Current smoking, excess body weight, being physically inactive, but not high alcohol consumption, were identified as the major lifestyle risk factors for AMI using Cox regression analysis. A competing AMI risk model built from cause-specific Cox regression models and considering the risk of death predicted 353 AMI cases, 182 (51.6%) of which were estimated as preventable through adherence to a healthy lifestyle profile (never smoking, normal body weight, physically active, and moderate alcohol consumption). The calculated age-specific 5-year incidence rates for AMI in the actual cohort and in a hypothetical, comparable cohort with all men following the healthy lifestyle profile were 128 and 39, respectively, per 100,000 person-years for the age group 40-44, increasing to 468 and 307 per 100,000 person-years for the age group 65-69. The estimated AMI incidence rates for men with the healthy lifestyle profile are still somewhat higher than the average rates reported for documented low-incidence regions, such as parts of Japan. Our analysis confirms the strong primary preventive potential for AMI based on avoidance of smoking and excess body weight, and on regular physical activity.