Idiopathic dilated cardiomyopathy is a severe disease with a high mortality rate in childhood. Its clinical evolution and prognosis are important for the selection of cardiac transplantation candidates. In order to characterize its evolution and identify prognostic factors, the clinical records of 41 children with the diagnosis of idiopathic dilated cardiomyopathy, admitted from January 1985 to December 1997, were reviewed. Survivors (Group I) and deceased (Group II) were separately analyzed, according to the following parameters: age, sex, race, clinical severity, electrocardiographic, echocardiographic and haemodynamic findings. Seven children were excluded from the study: six of them were lost to follow-up and one died from a surgical complication. Of the remaining 34 children, 20 were male (M) and 14 were female (F) (M/F: 1.4). Age range at diagnosis was 7 days to 14 years (median: 1.5 years), and follow-up time was from 18 days to 10.5 years (median: 2.5 years). Eleven (32.3%) children fully recovered, 13 (38.2%) survived with left ventricular dysfunction, and ten (29.4%) died, half of them within the first three months of follow-up. Mortality was 23.5% (8 out of 34 children) during the first year of follow-up and 29.4% (ten out of 34 children) at five years. Unfavorable prognosis was more frequently associated to: 1) clinical severity at the time of presentation; 2) lower mean left ventricular shortening fraction (10 +/- 7% in group II and 13 +/- 5% in group I); 3) occurrence of severe arrhythmia (40% in group II and 3.5% in group I). In this series a group of higher mortality risk was identified, based on some of the analyzed parameters, which should be considered as selection criteria for early heart transplantation.