• The role of Down syndrome (DS) in the outcome of the surgical correction of atrioventricular septal defect (AVSD) was investigated by the analysis of clinical events among 85 patients. Complete AVSD (cAVSD) was present in 49 patients, of whom 36 (73%) had DS. Thirty patients (83%) survived surgical treatment. Of the 13 patients without DS, 7 (54%) survived. There were four deaths and one late death. Thirty-six patients had partial AVSD (pAVSD), 5 (14%) of whom had DS; all 5 patients are still alive. Thirty (97%) of the 31 patients with pAVSD without DS survived the operation. There were two late deaths. Preoperative selection did not account for the favorable results in children with DS. All early postoperative deaths in cAVSD occurred in children younger than 2 years; low body weight for age seemed to be an important factor in adverse outcome. A large number of patients without DS had other serious congenital malformations. In view of the relatively favorable results in patients with DS, it does not seem warranted to maintain a conservative diagnostic and therapeutic approach of AVSD solely because of concomitant DS.