The purpose of our study was to evaluate the early phase hemodynamic changes in patients with clinically uncomplicated acute myocardial infarction. Detailed sequential hemodynamic evaluation is hardly available in the early phase of acute myocardial infarction in this group of patients as opposed to patients with complicated acute myocardial infarction. We evaluated sequentially the hemodynamics of 17 patients with uncomplicated acute myocardial infarction (Kilip class I). Cardiac output and ventricular ejection period were determined by impedance cardiography. All patients had an uneventful recovery, without clinical evidence of derangement of myocardial function as assessed by physical examination, chest X-ray and blood gases. Despite the uniformly uncomplicated convalescence, different hemodynamic patterns were found. Based on the hemodynamic data, patients were divided into two groups. In 10 patients no significant change in hemodynamic parameters was observed, while in 7 patients a significant decrease in cardiac output was found during the early post myocardial infarction period. Total peripheral resistance was significantly elevated in the group with decreased cardiac output. No relationship was found among location of infarction, creatine phosphokinase levels and hemodynamic outcome. A considerable proportion of patients with asymptomatic and uneventful convalescence after acute myocardial infarction have a decrease in cardiac output and a significant increase in total peripheral resistance which is not detected by routine clinical evaluation.