In a tertiary referral centre 63 patients underwent 67 treatment periods with enalapril. The median age was 5.4 months. All children had signs of heart failure: congestive cardiac failure with breathlessness at rest was present in 88%. Haemodynamic groups were left-to-right shunt (n = 15), impaired ventricular function (n = 14), after cardiac surgery (n = 23), valvar regurgitation (n = 12), and hypertension (n = 3). Serial clinical, radiological, and laboratory data were used to judge outcome. The mean (SD) maximal dose was 0.30 (0.21) mg/kg/day. Thirty nine (58%) patients improved, 20 (30%) showed no improvement, and eight (12%) had side effects requiring discontinuation of enalapril.