During a four-year period, aortic or mitral valve replacements with the Björk-Shiley tilting disc valve were performed in 114 cases. The series comprises 75 aortic, 34 mitral and 5 double valve replacements. In the aortic valve group (AVR) concomitant resection of the ascending aorta (cystic medial necrosis aneurysm)) was carried out in 5 cases, aortocoronary bypass in 2 cases and closure of a VSD in one case. Antibiotic prophylaxis and postoperative anticoagulant treatment were used routinely. The hospital mortality rates were6 8.0% in the AVR-group (single aortic valve mortality 7.1 %), 8.8% in the MVR-group and 60% in the double valve group. Late mortality in the AVR-group was 2.8%. There were no late thromboembolic complications in this group. Aortography showed grade II--III regurgitation (paravalvular leaks) in 15 % of the cases. In the MVR-group the late mortality was 9.7%. One patient died because of malfunction (thrombosis) of the prosthesis. The thrombotic complication was obviously caused by discontinuation of anticoagulant therapy. The clinically estimated functional capacity NYHA classification) improved considerably, especially in the MVR-group.