BACKGROUND: Valve replacement in children has many problems such as the durability of prosthetic valve, thomboembolism and hemorrhage. But recently, the necessity of valve replacement in children increased and the above problems were solved party. So the number of valve replacement in children increased progressively. RESULTS: Valve replacement in 47 children were done at Seooul National University Chidren's Hospital from March 1986 to July 1991. The patients were composed of 25 males and 33 females. 25 patients had congenital heart disease and 22 patients rheumatic heart disease. 45 patients received single valve repalcement, 2 patients double valve repalcement, and among all of them, 2 patients redo-replacement. The major valve lesion was mitral insufficiency and post-operative status in view of NYHA functinonal class was improved in most patients. The mechanical valves were applied to 45 patients and tissue valves to 2 patients. The indication of valve replacement were progressive increase in ventricular volume, major regurgitant fraction over grade III decrease in exercise tolerance and vegetation. The overall early mortality was 8.5% and late mortality 0%. There were post-operative complication rate of 30% and late complication rate 14%, and among the later, valve faliure was reported in 2 pantients and thromboembolism in 1 patient. The complication-free rate was 97.7% at post-operative 1 month, 91.3% at 12 months, 90% at 36 months and 60% at 48 months. 43 patients received anticoagulation and/or antiplatelet therapy, but there was no critical indication for this. CONCLUSION: These results suggest that cardiac valve replacement in children have been effective therapeutic modality even though various problems still remain, but we propose that sufficient long-term follow-up and clinical research be needed.