Several reports indicate the benefit of ACE inhibitors for patients with left ventricular systolic dysfunction after acute myocardial infarction (MI). We sought to determine the implementation of the treatment guidelines in patient samples from the general population. Furthermore we aimed to identify patient characteristics associated with the use of ACE inhibitors. Screening of two MI-registries allowed the identification of 226 MI patients with left ventricular dysfunction. Patients were considered to be eligible for ACE inhibitor therapy when a EF < or = 40% was documented in the patient records of cardiac rehabilitation clinics (REG-MI, n = 147) or detected by standardised echocardiography (KORA, n = 78). On average 5.5 years following MI, a standardised questionnaire and a detailed medical history was obtained. Specifically, information was collected regarding current medication and potential contraindications for ACE inhibitors. MI patients with LV dysfunction received ACE inhibitors in 62% (REG-MI) and 45% (KORA). The doses prescribed were substantially smaller than target doses used in the large-scale studies (REG-MI: 40 +/- 4%, KORA: 23 +/- 3%, % of target doses). Only 13% (REG-MI) and 3% (KORA) received more than 50% of the target dosage. Additionally, actual doses of the most frequently used ACE inhibitors were significantly different (captopril: 23 +/- 2%, enalapril: 42 +/- 5% of target doses). The likelihood of receiving ACE inhibitors was significantly higher in patients with written recommendation for such medication (odds ratio 6.02, confidence interval 1.93-20.16) and in patients visiting cardiologists (odds ratio 3.69, confidence interval 1.26-11.07) as revealed by multivariate analysis of the REG-MI database. Despite national and international guidance, a large proportion of MI patients with left ventricular dysfunction is not receiving ACE inhibitors, and when used, the doses prescribed are markedly smaller than target doses used in clinical trials that established the utility of these drugs. Medical care by cardiologists and written recommendation of ACE inhibition in patient records were independent predictors of a more appropriate prescription of ACE inhibitors.