BACKGROUND Although more than 170,000 Medtronic-Hall mechanical valvular prostheses have been inserted world-wide, long-term results are available on only a small percent of those valves inserted. METHODS A prospective data registry of all Medtronic-Hall cardiac prostheses inserted by one surgeon was used to identify 460 valves inserted during 391 operations from 1983 to 1994: single aortic (n = 210), single mitral (n = 115), or double aortic and mitral (n = 66) replacements, including three tricuspid valve replacements. Follow-up was sought five times in 10 years and was available for 280 (99%) of 283 survivors with only an isolated aortic or mitral Medtronic-Hall valve followed up for at least 1 year (1,246 patient years). RESULTS Hospital mortality was 4.6% (18 patients). Of 40 late deaths, eight were valve-related (0.6% per patient-year). The linearized rates of complications for aortic and mitral valve replacements (percent per patient-year) were, respectively: structural deterioration, 0 and 0; nonstructural dysfunction, 0.1 and 2.1; thromboembolism, 1.3 and 2.1; thrombosis, 0 and 0.2; anticoagulant-related bleeding, 1.7 and 1.9; and prosthetic valve endocarditis, 0.6 and 1.0. Actuarial freedom from reoperation at 10 years was 97% for aortic and 88% for mitral valves. CONCLUSIONS The Medtronic-Hall mechanical valvular prosthesis has excellent durability and acceptably low rates of valve-related complications and remains my mechanical prosthetic valve of choice for both aortic and mitral valve replacements.