Ebstein's malformation of the tricuspid valve is a rare but complex congenital cardiac lesion characterised by a variable degree of dysplasia and displacement of the proximal attachments of its inferior and septal leaflets from the true atrioventricular junction. The aim of our retrospective study is to report the risk factors for mortality, and to determine the clinical profile as seen in 52 cases diagnosed in our service between 1978 and 2002, concentrating in particular on the outcome for the neonatal patient. There were 26 females and 26 males, and the age at presentation ranged from 30 weeks gestational age to 46 years. We found 23 associated cardiac anomalies in 20 cases. Of the patients, 11 patients (21%) died. Actuarial survival at 30 years was 65%. Predictors of death included fetal or neonatal presentation, presence of associated defects, a grade within the Celermajer index of 3 or 4, and a cardiothoracic ratio equal to or greater than 65%. The diagnosis was made in the neonatal period in 24 patients, nine of whom died. Of the 15 survivors, only 4 are free of symptoms. Surgical treatment was undertaken in 9 patients, with a mortality rate of 33% without late deaths, with all the survivors being in good condition. The mean period of follow-up for the 41 living patients was 16.5 years. An arrhythmia of variable severity appeared during the evolution of 27 patients (66%). At present, only 7 cases are in the functional class III or IV of the grading system of the New York Heart Association, but 25 patients (61%) needed some medical treatment, meanly for arrhythmic events. Thus, fetal and neonatal presentation of Ebstein's malformation is associated with a poor outcome. Moreover, the echocardiographic appearance, marked cardiomegaly, and the presence of associated lesions are all risk factors for mortality. Arrhythmia and need of medical treatment are common in older children and adults. Survival after surgical treatment is associated with a good outcome.