The hypothesis that transvenous implantation of a cardioverter-defibrillator is associated with less morbidity than use of a transthoracic approach was investigated in a retrospective series of 146 patients. None of these patients had concomitant heart procedures, and the preoperative characteristics of the two groups were similar. When analyzed by actual technique used (transvenous, 57 patients; transthoracic, 89 patients) and by the intention-to-treat method (transvenous, 65 patients, 8 of whom actually underwent thoracotomy; thoracotomy, 81 patients), transvenous implantation was associated with a lower incidence of postoperative respiratory complications and atrial fibrillation. Total cardiac mortality and freedom from sudden cardiac death in the transvenous and transthoracic groups were comparable at 2 years.