The CarboMedics cardiac prosthesis (CarboMedics, Inc., Austin, Tex.) is a relatively new, low-profile bileaflet prosthesis. We report the results of a prospective mid-term evaluation of 426 CarboMedics prostheses implanted at our institution. Three hundred fifty patients had CarboMedics prostheses implanted in the mitral (n = 125), aortic (n = 149), or aortic and mitral positions (n = 76). Hospital mortality was 5.2%. Follow-up was 98% complete, with 478 patient/years and a mean follow-up of 19 months (range 1 to 42 months). Actuarial freedom from complications were calculated as follows (linearized rates in parentheses): late mortality 97% +/- 0.77% (2.7%), thromboembolism 98% +/- 0.4% (0.5%), anticoagulation-related hemorrhage 98.6% +/- 0.4% (0.4%), nonstructural dysfunction 98.5% +/- 0.6 (0.2%), valve-related mortality 91.5% +/- 0.7 (0.5%), valve failure 90.9% +/- 1% (0.7%), treatment failure 92.8% +/- 0.8% (0.7%), and all valve-related morbidity and mortality 90% +/- 2% (2.6%). According to our results, the CarboMedics valve has a low rate of complications that further improves the quality of life in patients with heart valve prostheses.