OBJECTIVE Postoperative left ventricular outflow tract obstruction (LVOTO) after arterial switch operation (ASO) is rare. In this retrospective study, we reviewed the cases of 10 patients with LVOTOs post-ASO and analyzed the options used for the LVOTOs corrections and the patients' outcomes. METHODS From December 1982 to December 2006, 1689 consecutive ASO were performed. Ten patients presented with postoperative LVOTOs (0.59% of all ASO and 7.62% of ASO for Taussig-Bing anomaly (TBA)) leading to reoperations. Before ASO they presented with significant subaortic gradients (n=4) or predisposing anatomical features (n=9) such as: conal septum malalignment (7/9), abnormal tricuspid cords insertions (4/9), muscular bundle hypertrophy (3/9) and mitral accessory tissue (2/9). RESULTS No patient was lost in the follow-up: 117+/-33 months. Subaortic gradients had developed between 5 months and 14 years after ASO (mean 41+/-35 months) leading to reoperations. Most LVOTOs post-ASO were due to fibrotic membranes or fibro-muscular hypertrophy, removed at first reoperation. After their first reoperations, seven patients (70%) had non-significant or low gradients and were not reoperated for LVOTO. Three patients underwent iterative surgical procedures for LVOTOs leading to two aortic valve replacements associated with LVOTO release or Konno procedure. CONCLUSIONS Postoperative LVOTO after ASO is rare but happens more frequently in TBA. Most of them can benefit from resections of subaortic obstacles or septal plasties. In more complex cases iterative surgical procedures may lead to complications such as block or severe aortic valve regurgitation.