A group of 300 institutionalized individuals, average age, 82 years, was followed from the onset or discovery of an intraveritricular conduction disturbance to death over an average period of more than five years. They included 143 cases with left anterior hemiblock, 60 cases with left bundle branch block, and 97 cases with right bundle branch block with and without left anterior or posterior hemiblock. Twenty-two cases developed second or third degree heart block. The magnitude of risk of developing second or third degree heart block averaged 1.5% per year for the first five years of follow-up and 2.5% per year for the next four years of follow-up. For the first five-year period of follow-up the magnitude of risk was 6.9%, and for the entire nine-year period of follow-up 15.7%. An intraventricular conduction disturbance was found before death in 20% of those dying in the institution. The causes of death among those with intraventricular conduction disturbances were similar to those of comparable age and sex without these conditions. Sudden death among those with second and third degree heart block was due in the majority of cases to other cardiac conditions, such as acute myocardial infarction and acute pulmonary embolization. It was concluded that the presence of an intraventricular conduction disturbance in the aged, uncomplicated by the development of second or third degree heart block, is not an indication for the insertion of a cardiac pacemaker in the aged.