One hundred and fourty-one Bjork-Shiley Monostrut valves were implanted in 105 consecutive patients from November 1983 to February 1990. There were 61 male and 44 female patients with a mean age of 33.6 years at the surgery. The cummurative follow-up was 370.3 patient-years with a mean of 44.0 months per patient. The operative mortality rate was 3.8%, and the linealized late mortality was 1.18%/patient-year. The incidence of major complications were 4.59%/patient-year, and the actuarial rate of freedom from valve-related morbidity was 80.2$pm$4.4% at 7 years. The 7-year survival rate was 90.5$pm$4.1%, and the actuarial rate of freedom from thromboembolism at 7 years was 93.3$pm$2.3%. The linealized annual rates of complication were ; structural valve failure 0.27% /patient-year, non-structural valve failure 0.54% /patient-year, thromboembolism 1.62% /patient-year; bleeding 1.62% /patient-year; endocarditis 0.54% /patient-year. On the basis of our experience, we judged the Bjork-Shiley Monostrut valve reliable, with similar incidence of valve-related morbidity of other mechanical prosthetic valves.