Valve replacement in children and adolescents, aging below 20 years [Mean 15 years 4 months], has been done at Seoul National University Hospital from March 1977 to September 1982 . Seventy-Seven patients have received 91 artificial valves 4 prosthetic valves and 87 bioprosthetic valves. 63 patients had acquired valve lesions and 14 patients had congenital valve lesions. Among the patients with acquired valve lesion, 32 patients had the history of rheumatic fever. Seventy-five patients survived operation: 12 patients [ 15.6%] died within one month postoperatively and 3 patients [3.9%] during the follow-up period with the overall mortality rate of 19.5% Thromboembolic complication occurred in 3 patients with 2 deaths: 3.9% embolic rate or 3.74% emboli per patient-year. One patient who had been on coumadin anticoagulation died from cerebral hemorrhage. Actuarial survival rate was 77.6% at 1 years after surgery, after then there were no death. [KTCS 1983;4:444-451]