Multiple system organ failure after cardiac surgery in children is a severe complication with unknown mid- and long-term sequelae. We therefore evaluated 11 children (aged 20-126 mo, median: 67 mo) having survived multiple system organ failure after cardiac operations for congenital cardiac defects in a cross-sectional follow-up study 12-76 mo (median: 32 mo) after surgery. Clinical and laboratory examinations included cardiac, pulmonary, renal, hepatic, neurological and psychological function tests. All patients had adequate cardiac function. Lung mechanics were abnormal in three children and glomerular renal function was abnormal in two patients. Slight elevation of gamma-glutamyl transpeptidase and coagulation factor deficiency was present in six and seven patients, respectively (five of whom had undergone the Fontan operation). Severe neurological sequelae such as diplegia (n = 1) and mental retardation (n = 1) were observed in two patients. In addition, five children presented delayed motor, graphomotor and/or speech development. Two children were found to have abnormal intelligence. We conclude that with the exception of neurological impairment, mid-term sequelae of multiple system organ failure after cardiac surgery in children are mild. However, longer follow-up using an appropriate control group is mandatory.