A total of and consecutive 87 patients underwent concomitant double mitral and aortic valve replacement with the St. Jude Medical prosthesis between January 1985 and December 1993. They were 44 males and 43 females with the ages ranging from 18 to 59 years[mean$pm$SD: 40.9$pm$9.5 years . Fifteen patients[17.2% had a history of previous cardiac valve replacement. There were 2 early deaths[2.3% , and 85 early survivors were followed up for a total of 352.6 patient-years[mean$pm$SD: 4.1 $pm$2.6 years . All were anticoagulated with coumadin keeping the target international normalized ratio within the range of 1.5 and 2.5. There was a single late death[late mortality of 0.284%/patient-year . Thromboembolism was the most frequent complication[1.985%/patient-year , and bleeding related to anticoagulation was experienced in one patient [0.284%/patient-year . The incidences of prosthetic valve endocarditis and of paravalvular leak were also low[0.284%/patient-year, respectively . The survival including operative mortality was 96.1%$pm$2.2% at 10 years. The actuarial probabilities of freedom from thromboembolism and from all events were 77.9%$pm$11.1% and 72.4%$pm$10.7%, respectively, at 10 years. There was no structural failure of the prosthesis. Results from a series of clinical studies suggest strongly that the use of lower intensity of anticoagulation therapy lowers the thromboembolic as well as bleeding rates in patients with the ST. Jude Medical prosthesis.