One hundred two patients, aged 0.7 to 38 years, with a wide variety of cardiac malformations underwent the Fontan operation (1975 to April, 1985). Several different techniques were used. All but 17 had previously undergone one or more palliative operations. Follow-up information was obtained in all patients. Overall actuarial survival rate, with time zero being the time of the operation, was 63% at 6 years with no deaths after that in patients followed as long as out to 9.4 years; that for patients with tricuspid atresia was 81%. The hazard function (instantaneous risk) for death was highest immediately after operation and merged after about 6 months with a constant hazard extending as long as the patients were followed. Elevated post-repair right atrial pressure was correlated (p = 0.002) with the probability of death in the early phase, with the risk rising rapidly with pressures above 14 mm Hg. Hypertrophy of the ventricular main chamber was a risk factor for death in both the early (p = 0.007) and late (p = 0.008) phases of hazard, which explained in part the lesser risk of the Fontan operation in patients with tricuspid atresia. Younger age, but not older age, was a risk factor for early postoperative death, but this risk was neutralized by recent date of operation. Thus currently there is not a predicted increased risk associated with younger age at operation. In general, the Fontan operation should be done at a young age (2 to 4 years) to avoid increasing ventricular hypertrophy, but older age per se is not a contraindication to the operation.