Transvenous cardiac pacing is now routinely used as therapy for heart block. As experience with transvenous pacing has increased, it has become apparent that a significant cause of pacemaker failure has resulted from malposition of the electrode catheter in the coronary veins. A simple technique ensures proper placement of the electrode catheter in the right ventricle by utilizing the intracavitary electrocardiogram. © 1971, American Medical Association. All rights reserved.