Mortality of pediatric patients with idiopathic dilated cardiomyopathy (IDC) is highest during the first 1 to 2 years the child is first seen. The echocardiograms of 72 infants and children with IDC were reviewed to determine whether left ventricular shortening fraction (LVSF), end-diastolic dimension, and wall mass were helpful in predicting outcome. Patients who were alive at last follow-up (group 1) were compared to those who died or required heart transplant (group 2). None of the indexes obtained at first examination were predictive of survival. Shortening fraction had improved significantly at follow-up 1 to 6 months after first examination in group 1 (15.1 +/- 0.9 to 24.4 +/- 1.8, p < 0.001) but remained unchanged in group 2 (14.1 +/- 1.5 to 15.3 +/- 3.2). No significant trends were noted in left ventricular end-diastolic dimension or wall mass. The 1- and 5-year actuarial survival for all patients was 75% and 60%, respectively. Persistent depression of LVSF < 15% was associated with a significantly lower survival rate (1-year 46%; 5-year 29%) compared to patients in whom follow-up LVSF was > 15% (1-year 97%; 5-year 90%; p < 0.05). It is concluded that the follow-up LVSF obtained at least 1 month after first examination is helpful in identifying pediatric patients who would benefit from early cardiac transplantation.