Thirteen patients out of 42 affected by acute myocardial infarction complicated by atrio-ventricular block survived the illness and were discharged from hospital. Eight of these patients (60%) died, all in the first six months of follow up: 3 suddenly and 5 in consequence of progressive heart failure. Dead patients were all in III or IV class of the N.Y.H.A. Three had been previously submitted to permanent pacing, one of these died suddenly. Five patients survive at the end of follow up that varies from 2 to 56 months. Of these five survivors 1 patient belong to the I class of the N.Y.H.A., 1 to the II class and 3 to the III class. Among survivors there is only 1 patient with permanent pacing. This is also the only one who had syncopal attacks during a period of pacing failure. Prognosis of patients with myocardial infarction complicated by atrio-ventricular block who survive illness is dependent on functional class and seems to be not considerably modified by permanent pacing.