The results of cardiac valve replacement with the Monostrut Björk-Shiley prosthesis (Shiley, Inc., Irvine, Calif.) during a 7-year period are presented. A total of 984 valves were implanted in 820 patients from May 1983 to April 1990. Aortic valve replacement was performed in 378 patients, mitral replacement in 294, and multiple replacement in 148. In addition, 180 patients (22%) underwent associated procedures. Mean age was 52.6 +/- 11 years. Operative (30 days) mortality was 5.9% (49 patients): 3.9% (15 patients) for aortic, 7.8% (23 patients) for mitral, and 7.4% (11 patients) for multiple valve replacement. All patients were given long-term anticoagulation therapy. Follow-up was 99% complete (eight patients were lost to follow-up), with a closing interval of 3 months, and totaled 2422 patient-years. Valve-related complications, expressed as percentage event-free (+/- standard error) at seven years were as follows: structural deterioration, 100%; nonstructural dysfunction, 98.3% +/- 0.6%; thromboembolism, 90.2% +/- 1.7%; anticoagulant-related hemorrhage, 88.7% +/- 2.8%; and prosthetic valve endocarditis, 98.1% +/- 0.8%. There were no cases of valve thrombosis. Actuarial survival (free from operative, valve-related, and sudden death) was 88.4% +/- 1.2% at 7 years. Freedom from reoperation was 96.8% +/- 0.1%. Probability of being free from all valve-related morbidity and mortality was 70% +/- 3%, and 708 (93%) of the survivors were in New York Heart Association class I or II. Serial Doppler echocardiograms were done prospectively in 243 patients (with 154 aortic and 120 mitral prostheses), both postoperatively and at regular intervals up to 3 years. Mean prosthetic gradients ranged from an average of 20.9 to 7 mm Hg in the aortic prostheses (21 to 29 mm) and from 6.1 to 4.8 mm Hg in the mitral prostheses (25 to 31 mm). The gradients in each patient did not change significantly during the follow-up period. Our 7 year's experience with the Monostrut valve shows a low rate of valve-related complications, a durable design, and good hemodynamic and functional results.