BACKGROUND The aim of this study was to assess by angiography the late effects of both classic and modified Blalock-Taussig shunts in terms of growth and development of stenosis and distortion. METHODS At a mean of 51 months postoperatively, we retrospectively reviewed the results in 78 patients who underwent creation of Blalock-Taussig shunts (25 classic and 71 modified). RESULTS At the level of the anastomosis, the shunt caused a reduction in diameter of the pulmonary artery in 49% of all shunts, major stenosis (>50% narrowing of the lumen) in 14%, and distortion of the pulmonary artery in 19%, findings that did not correlate with the type of shunt. Distortion did correlate with younger age at the time of shunt operation (p=0.01). CONCLUSIONS After a Blalock-Taussig shunt, growth of the pulmonary arteries occurred but did not exceed the normal growth of the pulmonary arterial tree. Moreover, a shunt procedure can cause distortion and stenosis of the pulmonary artery, which may have important implications for future corrective surgical intervention. All these findings support earlier complete surgical repair of correctable congenital cardiac defects.