Although most children after an arterial switch operation for transposition of the great arteries have normal development and cardiac function, a few require reoperation. During the last 10 years, 68 of 753 patients who underwent arterial switch operations (9.3%) underwent 75 reoperations. Thirty underwent early reoperation (< 30 days or during the same hospital stay) and 38 underwent late reoperation. Causes for reoperation included pacemaker insertion (n = 5), left diaphragm plication (n = 4), revision for hemostasis (n = 1), mediastinitis (n = 2), superior vena cava thrombosis (n = 9), subvalvular pulmonic stenosis (n = 5), supravalvular pulmonic stenosis (n = 16), residual atrial (n = 2) or ventricular (n = 8) septal defects, isolated mitral valve insufficiency (n = 2), aortic valve insufficiency (either isolated [n = 1] or in association with mitral incompetence [n = 1] or stenosis [n = 1]), left coronary artery ostial stenosis (n = 1), and recurrent aortic (n = 6) or neoaortic (n = 4) aortic coarctation. In all but 27 patients, the residual defects were already present immediately after the completion of the arterial switch operation; however, only patients with critical lesions were reoperated on early. Interventional catheterization procedures were performed when indicated; however, they only postponed inevitable reoperation. Successful relief of superior vena cava thrombosis was achieved by atriojugular bypass grafting in two patients, by early open thrombectomy in six patients, and by direct patch angioplasty of the superior vena cava once. Patch plasty for subvalvular or supravalvular pulmonic stenosis was carried out in 21 patients, septal defect closure was carried out in nine patients, and pulmonary artery banding was performed in one patient with criss-cross atrioventricular relationship and multiple ventricular septal defects. Valve repair was performed in all five patients with either isolated or combined aortic and mitral valve dysfunction. One patient with left coronary ostial stenosis underwent a patch enlargement of this ostium. Recoarctation was repaired by end-to-end anastomosis in eight patients and by a subclavian flap and a patch angioplasty in one patient each. Seven patients underwent a second reoperation for supravalvular pulmonary stenosis (n = 3), mitral valve replacement (n = 1), ventricular septal defect closure (n = 1), and recurrent coarctation (n = 2). There were six intraoperative (8.8%) and two late deaths. All early deaths occurred after early reoperations.(ABSTRACT TRUNCATED AT 400 WORDS)