Intraventricular conduction disturbances (IVD) were found in 181 (21,9%) out of 828 patients with acute myocardial infarction. Isolated RBBB was present in 6,3% of cases; both RBBB and LAH or LPH in 3,4%; isolated LAH in 5,8%; LBBB in 3%; suspect blocks of the three brances [RBBB+LAH+first degree atrio-ventricular block (AVB), or LBBB+first degree AVB] in 2,9% of cases. The severe mortality (41%) during hospitalisation of patients with IVB seems to be due to the haemodynamic impairement: cardiogrnic shock was observed in 20% of these patiens and acute pulmonary oedema in 18%. Transient or permanent complete AVB occurred during hospitalisation in 24,3% of these patients. The occurrence of complete AVB was higher (54%) in patients in whom suspect block of three branches was present. It was found that the progression of IVD to complete AVB increased the mortality rate to 48%. The short term prognosis of patients with IVD does not seem to be improved by prophilactic electrical stimulation, but the rate of deaths for asystolia is reduced. The mortality rate after one year of patients discharged from hospital was 25%; suspect three branches IVD died suddenly and 2 progressed to complete AVB. In the author's opinion the implantation of permanent electrical stimulation is indicated in patients showing IVD of the three branches assessed using His bundle electrgram during the acute phase of myocardial infarction.