AIMS: To evaluate the prognosis of patients > or = 80 years old, we analysed a large, community-based population with acute myocardial infarction who received intensive observation and similar pharmacotherapy regardless of age. METHODS AND RESULTS: In a 12-year period, before the introduction of thrombolysis, 4259 consecutive patients hospitalized with acute myocardial infarction from the same hospital in Denmark were prospectively registered. Their complications and mortality in hospital, and 1 and 5 years after discharge were analysed retrospectively. Overall, in-hospital mortality was 11% for patients less than < 50 years old, 22% for patients 60-69 years old and 43% for patients > or = 80 years old. Two thirds of patients > or = 80 years old had heart failure, and cardiogenic shock was twice as common in this age group than in patients 60-69 years. Heart failure was a strong independent risk, factor for post-discharge mortality, particularly in the oldest age groups. Four out of eight patients > or = 80 years survived one year if discharged alive after experiencing in-hospital ventricular fibrillation. CONCLUSION: The life-saving potential of preventing or treating heart failure seems considerable even in the oldest patient groups. Patients > or = 80 years old who survive in-hospital ventricular fibrillation have an acceptable prognosis 1 year post-discharge.