Between July 1979 and October 1984, 61 systemic-pulmonary arterial shunts were created in 45 patients. Clinical and angiographic results with 23 classic Blalock-Taussig shunts (BTSs) and 35 modified Blalock-Taussig shunts (MBTSs) with polytetrafluoroethylene grafts between the subclavian and pulmonary arteries were compared. Forty-three of the patients studied were infants: 28 were less than 1 month old, and 19 were less than 1 week old. Weights were 1.1 to 19 kg (mean 2.9 kg). Diagnoses were complex tetralogy of Fallot (18 patients), transposition of the great arteries with small left ventricle or left ventricular outflow tract obstruction (six patients) pulmonary atresia (seven patients) with intact ventricular septum (three) and ventricular septal defect (four), tricuspid atresia (four patients), univentricular heart (six patients), atrioventricular septal defect (canal) with pulmonary stenosis (three patients), and double-outlet right ventricle (one patient). Comparison groups were concurrent and were equivalent for age, weight, and complexity of anomaly. Patients were removed from the study population at the time of subsequent open heart surgery or at death. All patients were followed for a minimum of 6 months and for up to 5 1/2 years (BTS 1 1/2 to 5 1/2 years, mean 33 months; MBTS 6 months to 3 years, mean 20 months). There were no intraoperative deaths in either group. Among the 23 BTSs, three failed at 1, 3, and 19 days, resulting in two deaths (17%). One premature infant died despite a second shunt, one died during attempted intracardiac repair at 13 days of age, and the other was well after revision of the shunt. Eight patients underwent subsequent intracardiac repair 1 to 5 years (mean 34 months) after the initial procedure. Another four patients died from complex intracardiac anomalies with patent shunts. Three patients are alive 2 to 4 years after receiving shunts and have not undergone subsequent surgery. Late postoperative angiograms demonstrate a disturbing incidence (21%) of stenosis and right pulmonary arterial deformity despite satisfactory immediate postoperative studies and good clinical function. Eight patients required a second shunt, two for anatomic discontinuity of the pulmonary arteries and six because of inadequate blood flow through the first shunt. Among the 35 patients receiving the MBTS, two required early revision (technical error and ductal tissue at the anastomosis). There were no shunt-related deaths, but three (6%) occurred within 30 days of operation from left ventricular infarct, cerebral hemorrhage, sepsis, and severe aortic stenosis with arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)