The aim of this study was to assess the hemodynamic response to intravenous atenolol in elderly patients with acute myocardial infarction. We studied 14 elderly men, aged 64-85 years, and 14 younger men, aged 29-48 years, in the early postfibrinolytic phase of acute myocardial infarction. All the patients were in Killip class I. A triple-lumen Swan-Ganz thermodilution catheter was introduced into the right heart chambers. The patients received 5 mg intravenous atenolol over 5 minutes. All hemodynamic parameters were measured before and 10 minutes after atenolol. The hemodynamic characteristics and the location and extent of acute myocardial infarction were the same in both groups before atenolol. The hemodynamic changes after atenolol administration were the same in the two groups, but the stroke volume and cardiac indexes decreased to a greater extent in the elderly (p = .01 and p = .0001, respectively). These results indicate that intravenous atenolol in the early postfibrinolytic phase of acute myocardial infarction is safe in Killip class I elderly patients, although the cardiac and stroke volume indexes decrease, and the increase in the total systemic resistance is more in older than in younger patients.