The short- and long-term results of provisional pacemaker therapy in fresh myocardial infarction have been investigated. In this cardiac unit in the period 1975--1977 provisional pacemakers were implanted in 48 patients due to severe conduction disturbance or sinus node syndrome with non-tolerated heart failure. 16 patients had bifascicular block (11 anterior, 3 diaphragmatic, and 2 non-localizable infarctions): in 9 (56%) of them, progression to complete AV block occurred. 27 patients exhibited AV block of 2nd to 3rd degree without evidence of fascicular blockades (21 diaphragmatic, 3 anterior, and 3 non-localizable infarctions). In 5 patients, sinus node dysfunction was the reason for pacemaker implantation. Hospital mortality in the group was 31.2% and thus was twice as high as the hospital mortality in all patients hospitalized in this unit with myocardial infarction during the same period (16.5%). The hospital mortality in patients with anterior infarction was 57.2% compared with a mortality of 16.7% in patients with diaphragmatic infarction. Late mortality (18 months after myocardial infarction) in the group was 46.8%. None of the patients with diaphragmatic infarction died during this observation period. In the patient group with anterior infarction, the mortality rose to 85.8%. Of the 14 patients who died in hospital, death in 12 was due to severe heart failure: neither bradycardic nor tachycardic arrhythmias were immediate factors in death. At autopsy, all patients exhibited severe coronary sclerosis with extensive myocardial infarction. Only 2 patients died from arrhythmia (atrial fibrillation/asystole). In 6 of the 34 survivors, a definitive pacemaker was implanted. 3 of these patients died in the first year after the myocardial infarction. Death was sudden in all three.