Forty two children with end stage renal failure and hypertension on chronic haemodialysis have been treated with captopril for from 18 to 78 months. Satisfactory control has been obtained in doses of 0.3 to 3.0 mg/kg given every 24 or 48 hours. Tolerance was good. The results of the present study suggest that captopril is a suitable drug for long-term use in paediatric patients.