Results of St. Jude Medical valve replacement are presented in 171 patients who underwent operation from January 1983 through June 1989. The patients were 79 males and 92 females with ages ranging from 12 to 71 years. Total 211 of St. Jude Medical valves were implanted: 148 in mitral position, 57 in aortic position, 6 in tricuspid position. The follow-up was from 2 to 76 months with a cumulative period of 375 patient-year. The actuarial survival at 1 year, 3 year and 5 year were 92.1 %, 87.6 % and 86.3% respectively. The linearlized incidences of valve failure, thromboembolism, thrombotic obstruction, anticoagulation related hemorrhage and all valve related complication were as follows: 0.5 %/pt-yr, 0.5 %/pt-yr, 0.5 %/pt-yr, 1.1 %/pt-yr, and 2.4 %/pt-yr, respectively. The performance of the St. Jude Medical valve compares most favorably with other artificial valves. But it remains still hazards of mechanical prostheses such as thromboembolism and thrombotic obstruction.