Percutaneous balloon angioplasty was successful initial treatment for 2 infants who, early after operation, developed obstruction at the proximal anastomotic site of a modified Blalock-Taussig shunt. Two years later the first child had not required reoperation and the dilatation site was patent angiographically. The other baby progressed well after angioplasty but because of surgical concern about the long-term success of angioplasty, shunt surgery was repeated, the baby dying after reoperation. Angioplasty of proximal obstruction in these shunts is feasible and satisfactory long-term palliation can be achieved avoiding repeat shunt surgery before the more definitive Fontan-type procedure.