Since 1985, 354 neonates have undergone palliative reconstruction for hypoplastic left heart syndrome with 109 early deaths and 12 late deaths. Of the survivors, before 1989, 77 patients underwent a subsequent modified Fontan operation, consisting of baffling the atrial septal defect to the tricuspid valve (initial 25 patients) or intraatrial baffling of the inferior vena cava to the pulmonary arteries and superior vena cava (52 patients). There were 17 early deaths and three late deaths. Major serous effusions developed in 42 patients (54%) after Fontan operation. Since 1989, a staged approach to Fontan's operation was undertaken in an effort to reduce the volume load of the right ventricle as early as possible, to minimize the impact of rapid changes in ventricular geometry and diastolic function that can accompany a primary Fontan operation, and to reduce effusive complications. Thus, at a mean age of 6 months, 121 patients have undergone closure of aortopulmonary shunt, augmentation of central pulmonary arteries, and association of the superior vena cava with the branch pulmonary arteries (hemi-Fontan procedure). Of these, 61 patients have already undergone completion of the Fontan procedure with six early deaths and three late deaths. Major serous effusions developed in 28 patients (46%) with the staged Fontan. For perspective, the contemporary experience since January 1991 consists of 58 neonates who have undergone initial palliation with 11 deaths (19%), 17 patients who have undergone the hemi-Fontan procedure with one death (6%), and 21 patients who have undergone completion of the Fontan operation with one death (5%).(ABSTRACT TRUNCATED AT 250 WORDS)