Background: Grown-ups with congenital heart disease (GUCH) are an increasingly important group of patients, with many requiring reoperations because of late complications or residual defects, correction after palliation, further palliation or heart transplantation. Methods: In order to identify perioperative risk factors, we have retrospectively analysed perioperative mortality and morbidity of 66 consecutive GUCH patients needing reoperations between July 1987 and December 2000 with a mean age of 28±12 (14.2–63.5) years and preoperative ejection fraction of 57±21%. Primary cardiac defects were LVOT pathology (17 patients), coarctation (10), Tetralogy of Fallot (TOF) (9), VSD (9), transposition of the great arteries (TGA) (7), Marfan syndrome (6), ASD (5) and others (3). Results: Reoperations included various aortic valve procedures (28), aortic replacements (16), ASD/VSD closures (16), conduits (11), RVOT procedures (8), coarctation repair (5), cardiac transplantation (3) or others (8). Early mortality was 7.6%. Serious postoperative complications occurred in 24%. Presence of cyanosis, heart failure, VSD, TGA, pulmonary atresia, correction after palliative surgery and number of previous operations were preoperative risk factors and duration of operation, cardiopulmonary bypass and aortic cross-clamp, core temperature, low output syndrome, use of epinephrine, pneumonia and ARDS, renal failure, dialysis and stroke perioperative risk factors for fatal outcome. Conclusions: Reoperations in GUCH patients are mostly due to outflow tract lesions, coarctations and TOF. Perioperative risks remain important especially with cyanosis, TGA, pulmonary atresia and poor ventricular function. Therefore, close follow-up, timely referral for re-intervention and adequate perioperative management are mandatory to reduce perioperative risks and improve results.