The fate of 191 infants with double-inlet ventricle was studied to determine the influence of morphologic characteristics at presentation and subsequent management on the potential for, and timing of, definitive repair by the Fontan operation or ventricular septation. At presentation, 136 patients (71%) were potential candidates for a Fontan procedure. Actuarial survival was better than for those deemed unsuitable for either definitive option (n = 55; 68% versus 28% at 1 year; p less than 0.001), but still, only 78 patients (57%) were known to be alive and suitable candidates at 2 years of age. This was largely due to death after presentation with low cardiac output (n = 19) and at palliative operation (20 of 98 surgically treated patients). The adverse events of late sudden death (n = 14) and the development of new features precluding a Fontan operation (n = 18) mostly occurred before 4 years of age (n = 22). Patients requiring no operation and those who underwent a systemic-pulmonary arterial shunt fared better than those who underwent isolated banding of the pulmonary trunk (9/13 and 25/42 alive and suitable versus 14/33; p less than 0.05), and than those who required aortic arch repair together with banding (1/12; p less than 0.01), because of the development of subaortic stenosis in the latter group. In contrast, only 43 patients (23% of all 191 patients) had morphologic features that were additionally compatible with future ventricular septation. Actuarial survival free of adverse events for these 43 patients was similar to that of the 136 patients considered suitable for a Fontan operation. Thus management in infancy must be aimed at maintaining potential for a future Fontan operation, which itself should not be delayed, for most patients, beyond 3 years of age, because of the prevalence of adverse events with increasing age.