Over the 3-year period from Jan. 1, 1986, through Dec. 31, 1988, we have implanted 101 automatic implantable cardioverter-defibrillators into patients with life-threatening ventricular arrhythmias. There were 82 male patients and 19 female patients. The mean age was 58 years with a range of 25 to 82 years. The indication for implantation was ventricular fibrillation in 89 patients and recurrent ventricular tachycardia in 12 patients. Seventy-seven patients had a history of prior myocardial infarction or coronary artery disease, or both. Eighteen patients had nonischemic cardiomyopathy. One patient had a prolonged QT syndrome and five patients had no evidence of preexisting structural heart disease. The mean injection fraction was 37% +/- 17%. Forty-one of the automatic implantable cardioverter-defibrillator implantations were associated with procedures necessitating cardiopulmonary bypass. The hospital mortality rate was 4% and the morbidity rate was 15%. The only statistical difference between those patients who did and did not have postoperative complications was a history of a prior myocardial infarction (90% versus 54%, p less than 0.05). Twenty percent of patients had new-onset postoperative atrial fibrillation after implantation of the device. Eleven percent of patients had sustained ventricular tachycardia postoperatively. Although there was a trend toward a higher complication/death rate in the patients whose automatic implantable cardioverter-defibrillator was inserted in association with cardiopulmonary bypass (24% versus 15%) and the occurrence of new-onset postoperative atrial fibrillation (27% versus 15%), these findings were not statistically significant. Automatic implantable cardioverter-defibrillator implantation with and without concomitant cardiopulmonary bypass is associated with a clinically important morbidity and mortality rate and development of postoperative arrhythmias.