The automatic implantable defibrillator (AID) has been shown to prevent sudden death but it frequently gives rise to complications. These complications seem to be costly but they do not figure in the economic assessments of AID. From 1989 to 2003, 202 patients (173 men, age 58 +/- 14 years) received consecutively 264 AID in the same centre of implantation. The authors studied the complications of these implantations. The medical indication was secondary (documented spontaneous ventricular tachycardia or fibrillation) in 145 patients (71.8%) and prophylactic in the remaining 57 patients (28.2%). During the 36 month (+/- 35) follow-up, 40.6% patients had an appropriate treatment: 50.3% in the secondary prevention group versus 15.8% in the prophylactic implantation group. The one year, 5 and 15 year survival rates were 99, 88 and 85% respectively. Eighty seven complications were observed resulting in a long term complication in 36.7% of patients. These complications were: inappropriate electric shock, n=24 (27.6%), fractured catheters, n=12 (13.6%), haematomas, n=12 (13.6%), loss of function of the AID, n=10 (11.4%), infection, n=6 (6.8%), pneumothorax, n=7 (8.0%), and others n=16 (18.4%). The cost of these complications was assessed in terms of hospital stay in intensive care (1010.40 euros per day) or in the general cardiology wards (546.70 euros per day). The complications resulted in 502 days of additional hospital stay (5.77 days per complication) with a total cost of 285 655.20 euros (3283.40 euros per complication). The most expensive complications in terms of hospital stay were: infections (24.5 days), fractured catheter (5.75 days), and postoperative haematoma (5.5 days). These results indicate a significant cost of complications which should be indicated in the economic evaluation of AID.