From April 1, 1979 to August 31, 1983, 228 patients underwent isolated aortic (AVR) (118) or mitral (MVR) (90) valve replacements with a new tilting disc valve prosthesis, the St. Jude prosthesis, at the Medical University of South Carolina. Age ranged from 6 to 84 years (mean 49.1 +/- 19.2 AVR, 44.5 +/- 16.5 MVR). Male sex predominated in the AVR group (68%) and female sex in the MVR group (68%). Thirty-five patients (16.8%) had associated coronary bypass surgery (AVR 23.7%, MVR 7.8%). There were seven deaths (3.4%) occurring during the same hospitalization (AVR: 3/118, 2.5%; MVR: 4/90, 4.4%). Follow-up is 97.6% complete and ranges from 1 to 54 months (mean 19.6 +/- 12.4). In the AVR group, nine late deaths have occurred and actuarial survival at 42 months is 86.7 +/- 3.8%. Three patients have sustained thromboembolic episodes for a linearized rate of 1.6% patient-year, and the probability of remaining free of thromboembolism at 42 months is 96.9 +/- 1.8%. The mean improvement in functional class from preoperative to postoperative is 3.1 +/- 0.7 to 1.2 +/- 0.4 (p less than 0.001). In the MVR group, there have been four late deaths, and the actuarial survival at 42 months is 89.3 +/- 3.8%. Two patients have sustained thromboembolic complications for a linearized rate of 1.2%/patient-year, and the probability of remaining free of thromboembolism at 42 months is 97.2 +/- 2%. The mean improvement in functional class from before to after surgery is 3.2 +/- 0.7 to 1.3 +/- 0.5 (p less than 0.001). There have been no thromboses of the St. Jude valve in the mitral or aortic position, no mechanical failures, and no patient has had significant valve-related hemolysis. Because of this experience, the St. Jude Medical heart valve prosthesis is our prosthesis of choice for any patient undergoing valve replacement with a mechanical prosthesis.