Young age, low weight, and the requirement for transannular patch reconstruction of the right ventricular outflow tract (RVOT) are thought to adversely affect intracardiac repair of tetralogy of Fallot. Forty patients underwent complete repair between January, 1984, and January, 1987. Only infants with pulmonary atresia, complete atrioventricular canal, or coronary artery anomalies were shunted initially. The malalignment ventricular septal defect was closed with a Dacron patch. Infundibular resection was minimized. All atrial communications were left open. Thirty-four patients (85%) had a transannular RVOT patch, and 2 patients (5%) had a nontransannular patch. All 10 infants weighing 3.4 to 9.6 kg had a transannular RVOT patch at 7 weeks to 12 months of age. An RVOT patch was used in 26 of 30 children operated on between 1 and 6 years of age (median age, 24 months). No patient undergoing intracardiac repair died. Postoperative RVOT pullback gradients were between 0 and 35 mm Hg (mean, 18.5 mm Hg). Postoperative pulmonary artery saturation (mean, 73%) did not reveal any residual ventricular septal defect. The right ventricular/arterial pressure ratio was always less than 0.6 (mean, 0.4). All children are doing well at follow-up from two to 37 months. Serial echocardiograms reveal no residual ventricular septal defect and only 1 moderate RVOT gradient. Follow-up cardiac catheterization in 15 patients revealed no residual ventricular septal defect and RVOT gradients between 5 and 35 mm Hg. The right ventricular/left ventricular pressure ratio was always less than 0.6 (mean, 0.48). The early and late results justify continued primary repair of tetralogy of Fallot in symptomatic children, regardless of age or weight.(ABSTRACT TRUNCATED AT 250 WORDS)