Long-term left atrial pacing was successfully accomplished in three patients by positioning permanently implanted pervenous pacemaker catheters in the proximal portion of the coronary vein. Left atrial stimulation was documented by the configuration of the P waves on the electrocardiogram—the P waves were inverted in leads I and V6 and upright in V1. Roentgenograms of the chest revealed that the pacemaker electrodes were located inferiorly and posteriorly to the left atrium. In one patient, angiocardiography was used to document the position of the catheter in the coronary vein. One patient died of causes unrelated to the pacemaker one month after implantation, and the catheter tip was located in the coronary vein which was not thrombosed. The other two patients are doing well 13 and 18 months, respectively, after pacemaker placement, and consistent and stable atrial pacing has continued throughout this period of time.