BACKGROUND Efficacy and safety of primary percutaneous coronary angioplasty (PCI) in elderly patients with acute ST-elevation myocardial infarction (STEMI) have not yet been definitely established because these patients were usually excluded from large randomised trials. AIM To evaluate in-hospital and one-year outcome after primary PCI in elderly patients, and to assess clinical characteristics of this group. METHODS The study population included 1061 consecutive STEMI patients, mean age 60.6+/-17 years, treated with primary PCI. Clinical characteristics and results of 127 patients aged > or = 75 years were compared to the younger group. RESULTS Elderly patients were more frequently female (48.4 vs. 23.6%, p <0.005) and diabetics (22.2 vs. 12.1%, p <0.02) and more frequently had renal and/or left ventricular failure (22.3 vs. 9.1%, and 9.1 vs. 4.5%, p <0.005, respectively). In older patients less frequently stents were implanted and TIMI flow 3 was restored (65.1 vs. 78.8%, p <0.05 and 74.6 vs. 84.7%, p <0.03). In-hospital mortality in older versus younger patients was 11.8 vs. 3.0%, p <0.005. The incidence of in-hospital complications (stroke, major bleeding and reinfarction) was similar in both groups. The one-year mortality and MACE rates were higher in older patients (21.3 vs. 6.0% and 24.9 vs. 11.0%, p <0.0005). In multivariate analysis Killip class II-IV (OR 6.73; 95% CI 1.75-25.97, p=0.006) and heart rate (OR 1.04; 95% CI 1.01-1.07, p=0.03) were independent predictors of one-year mortality in patients aged > or = 75 years. CONCLUSIONS Primary PCI in older STEMI patients is associated with a favourable in-hospital and one-year outcome, although inferior to that seen in younger patients. The in-hospital complication rate is similar in the elderly and in younger patients.