One hundred thirty patients have had 244 pacemakers of five types implanted at Presbyterian-St. Lake's Hospital in the past eight years. There has been a 0.50 probability of successful unit function at only 12 months with epicardial units. All transvenous units used have had a 0.50 probability of unit success at more than 17 months. This fact, combined with the lower frequency of early death with transvenous units, has led to our opinion that epicardial units no longer have a place unless a thoracotomy is mandatory for other reasons. The data of the present study suggest an augmented early mortality with fixed rate transvenous units compared with a unit which synchronizes with the intrinsic ventricular rhythm. This, with the comparable unit reliability, will lead us to use ventricular synchronous transvenous units increasingly in the future. One hundred thirty patients have had 244 pacemakers of five types implanted at Presbyterian-St. Lake's Hospital in the past eight years. There has been a 0.50 probability of successful unit function at only 12 months with epicardial units. All transvenous units used have had a 0.50 probability of unit success at more than 17 months. This fact, combined with the lower frequency of early death with transvenous units, has led to our opinion that epicardial units no longer have a place unless a thoracotomy is mandatory for other reasons. The data of the present study suggest an augmented early mortality with fixed rate transvenous units compared with a unit which synchronizes with the intrinsic ventricular rhythm. This, with the comparable unit reliability, will lead us to use ventricular synchronous transvenous units increasingly in the future.