Background. We evaluated all adult St. Jude mechanical valve recipients at our institution since the initial implant in January 1979 and now present our 25-year experience. Methods. Nine hundred forty-five valve recipients were followed prospectively at 12-month intervals from January 1979 to December 2007. Results. Operative mortality was 3% in the aortic valve recipients and 5% in the mitral valve recipients. Follow-up was 95% complete. Among aortic valve recipients, late actuarial survival was 81% +/- 2%, 59% +/- 2%, 41% +/- 3%, 28% +/- 3%, and 17% +/- 4% at 5, 10, 15, 20, and 25 years, respectively. Twenty-five-year freedom from reoperation, thromboembolism, bleeding, and endocarditis was 90% +/- 2%, 69% +/- 5%, 67% +/- 3%, and 9% 3 +/- 2% respectively. Among mitral valve recipients late actuarial survival was 84% +/- 2%, 63% +/- 3%, 44% +/- 3%, 31% +/- 3%, and 23% +/- 4% at 5, 10, 15, 20, and 25 years, respectively. Twenty-five-year freedom from reoperation, thromboembolism, bleeding and endocarditis was 81% +/- 10%, 52% +/- 8%, 64% +/- 6%, and 97% +/- 1%. Freedom from valve-related mortality and morbidity at 25 years was 26% +/- 7% and 29% +/- 6% for aortic and mitral valve replacement, respectively. Freedom from valve-related mortality was 66% +/- 8% and 87% +/- 3% for aortic and mitral valve replacement, respectively. Conclusions. These results compare favorably with those for other mechanical prostheses. After two and a half decades of observation with close follow-up, the St. Jude mechanical valve continues to be a reliable prosthesis. (Ann Thorac Surg 2010;89:1402-9) (C) 2010 by The Society of Thoracic Surgeons