Over a 33 year period, 127 patients under 2 years of age with dilated cardiomyopathies and appearances compatible with the diagnosis of primary endocardial fibroelastosis were admitted to the paediatric cardiac unit of the CHRU of Lille. The average follow-up was 8.9 +/- 6.7 years. Ninety-four children (74%) were cured, 16 (13%) had persistent cardiomegaly and/or left ventricular dysfunction on echocardiographic examination, and only 17 (13%) patients died (10 in the year following their initial hospital admission including 5 in the first week). The outcome of patients was not related to age at diagnosis, sex, cardiothoracic index, initial shortening fraction of the left ventricle or the period at which the patients were seen for the first time. On the other hand, the presence of a family history of cardiomyopathy was associated with a significantly worse prognosis. A recurrence of symptoms was the factor most closely correlated with a bad prognosis: 12 of the 19 patients (63%) with this evolution died, and 4 others (21%) had persistent myocardial dysfunction at the end of the study. These recurrences were often observed after premature withdrawal or after use of ineffective dosages of digitalis. In the authors' experience, dilated cardiomyopathy in neonates with clinical features of primary endocardial fibroelastosis is associated with a relatively high number of cures. Prolonged treatment with high doses of digitalis seems a determining prognostic factor.(ABSTRACT TRUNCATED AT 250 WORDS)