The St. Jude Medical cardiac valve is a low-profile, bileaflet, central-flow prosthesis made entirely of pyrolytic carbon. A total of 261 St. Jude valves were implanted in 253 patients during a 25-month period. Perioperative mortality for the entire series was 9.1%, including patients undergoing reoperation for valve disease and those having associated cardiac procedures. There were four nonfatal thromboembolic episodes during the follow-up period, resulting in a risk of thromboembolism for aortic and mitral valves of 2.1% and 2.1% per patient year, respectively. There were no instances of structural failure of the valve, and no valve-related hemolysis occurred. Two-year actuarial survival was 95%. Hemodynamic studies indicate that the valve has the lowest transvalvular pressure gradient of any prosthetic mechanical valve available, and we believe it is the valve of choice for patients in whom a prosthetic mechanical valve is indicated.