The purpose of our study was to ascertain the outcome of the construction of a Blalock-Taussig shunt in patients aged 12 years and over. We identified 21 patients in whom a Blalock-Taussig shunt had been constructed subsequent to the age of 12 years. Of the patients, 9 were female, and their median age was 18.5 years, with a range from 12 to 46 years. All had usual atrial arrangement, and the atrioventricular connections were concordant in 11, with univentricular atrioventricular connection in 10. Pulmonary atresia was present in 8 (38 per cent), and pulmonary stenosis, either valvar or subvalvar, in 13. An interposition graft had been placed between the subclavian and pulmonary arteries in 16 patients, and an end-to-side anastomosis between the arteries in 5. One patient had died in hospital, while 4 patients had died during the period of follow-up after initial construction of the shunt. Long-term follow-up was available in 86 per cent of patients. In the 3 patients lost to follow-up, the shunt had been known to be functioning at periods of 4, 8, and 10 years, respectively. Actuarial freedom from death after a period of 17 years was 76 per cent. In 8 patients, a period of 10 years had elapsed with the shunt patent, and a further 10 had a patent shunt after 5 years follow-up. Symptomatic improvement was reported in 16 (76 per cent) patients, although adverse cardiac events had occurred during follow-up in 17, including congestive heart failure in 3, atrial fibrillation in 3, and endocarditis in 2. In 2 patients, it had been possible to proceed to biventricular repair, one with tetralogy of Fallot, and the other having a Rastelli procedure. Further in 3 patients, it had been possible to construct the Fontan circulation, or one of its variants. One patient has undergone cardiac transplantation, while 2 are awaiting transplantation. Symptomatic improvement can be achieved by construction of a Blalock-Taussig shunt in older subjects, and the risks of surgery are low. Later repair may be feasible in some patients, but adverse cardiac events may follow the increased volume load on the systemic ventricle.