Since 1979, 50 children, 4 months to 15 years of age, have successfully undergone cardiac valve replacement with the St. Jude Medical prosthesis (St. Jude Medical, Inc., St. Paul, Minn.). There were 24 boys and 26 girls. The valve replaced was mitral in 28 children, aortic in 15, mitral and aortic in 1, and mitral and tricuspid in 1. A left-sided tricuspid valve was replaced in 3 children. Anticoagulant therapy was maintained in all children; 40 children were treated with warfarin, whereas 10 children who underwent aortic or mitral valve replacement were on a regimen of aspirin combined with dipyridamole. The follow-up period, comprising 224 patient-years, ranged from 1 to 10 years. There were four valve-related complications: one from thromboembolism, two from valve thrombosis, and the other one from prosthetic valve endocarditis. Actuarial rate free from all valve-related complications at 10 years was 84.7%. There were four late deaths: one from valve thrombosis and the others from non-valve-related complications. Actuarial survival rate at 10 years was 90.8%. All surviving children are in functional class I, and no child so far has needed replacement of a prosthesis because of somatic growth. These results indicate that the St. Jude Medical prosthesis is a cardiac valve substitute of choice for valve replacement in children.