Thrombosis and occlusion of major veins have been described following the use of transvenous pacing electrodes for the establishment of permanent cardiac pacing. The frequency of such complications is, however, not well known. A series of 125 patients was therefore reviewed, all of whom had been paced with permanent transvenous electrodes through a cephalic vein. There was clinical and venographic evidence of subclavian vein occlusion in only 3 of these patients. A further 20 of these patients were also subjected to venography and showed no radiographic evidence of venous occlusion although minor thrombosis associated with the pacemaker electrode was found in one patient. It is concluded that the convenience of using the cephalic vein as a route for the insertion of transvenous pacing electrodes outweighs the small risk of major venous occlusion.