Congenital complete atrioventricular block is an uncommon disorder with a prognosis which is usually favorable. The disorder is sometimes associated with syncope, sudden death or cardiac pacing. It is difficult to determine the patients at risk of sudden death. In this retrospective study, hospital records of children who had been admitted to the Hacettepe University Children's Hospital between 1970-1990 for evaluation of complete heart block were examined. The study population, consisting of 39 children, 27 males and 12 females, had electrocardiograms consistent with complete heart block. These patients, diagnosed as having congenital complete A-V block, had an otherwise normally structured heart, and were followed up for a period of from one month to 15 years. Age at diagnosis ranged from 27 days to 17 years (mean: 86.9 +/- 48 months). Of the 14 patients with symptoms (five with syncope, eight with exercise intolerance and one with presyncope), nine were paced electively and have done well. Clinical and laboratory features of the asymptomatic and symptomatic groups were compared to evaluate potential risk factors.