A newborn with pulmonary atresia with ventricular septal defect and transposition of the great arteries was palliated with a modified Blalock-Taussig shunt at 5 days of age. Three days postoperatively arterial oxygen saturations dropped significantly. Thrombosis of the shunt was suspected. Angiography revealed stenosis of the proximal subclavian artery related to the creation of the shunt. The patient was successfully treated with angioplasty and stent implantation into the stenotic subclavian artery. Follow-up angiography 3 months after stent deployment showed a completely patent subclavian artery and unobstructed blood flow across the modified Blalock-Taussig shunt.