OBJECTIVE--To determine the incidence of infection after implantation of a cardioverter-defibrillator and the management of this complication. SUBJECTS--335 consecutive patients who had a cardioverter-defibrillator implanted between January 1984 and December 1993. MAIN OUTCOME MEASURES--Incidence of infection within the first month after implantation (early infection) and after the first month (late infection). RESULTS--Infections associated with cardioverter-defibrillator devices occurred in 13 patients (3.9%) during a mean follow up of 22 (11) months. All patients had general signs of inflammation, fever (> 37.5 degrees C), and leucocytosis (> 10,000/ml) with or without purulent drainage. Five patients (38%) had infections during the first implantation, whereas eight patients (62%) had infections after replacement of the pulse generator. Early infection was observed in four patients (31%) and late infection in nine (69%). Incidence of infection was higher in patients who underwent epicardial cardioverter-defibrillator implantation (12/207 patients, 5.8%) than in those who received nonthoracotomy lead systems (1/125 patients, 0.8%) (P < 0.05). Infections were caused by staphyloccocus in 10 patients, pseudomonas in two patients, and streptococcus in one patient. The whole device had to be removed in all patients. During a mean follow up of 39 (29) months seven patients died: six of congestive heart failure and one of myocardial reinfarction. CONCLUSIONS--Infection, one of the most serious complications after cardioverter-defibrillator implantation, is associated with increased morbidity and mortality. When infection occurs the system must be removed to avoid a fatal outcome.