Careful follow up studies in patients receiving a Silzone-coated St. Jude Medical valve (67 aortic valves, 36 mitral valves, nine double valves) did not support the fear of a high risk of perivalvular leak and embolism rate. Freedom from perivalvular risk at 12 and 24 months follow up was 98.5+/-1.5% and 100% for the aortic and mitral valves, respectively. Freedom from any thromboembolic event was 96.6+/-2.4% at 12 and 24 months follow up in the aortic group, and 97+/-3% at 12 and 24 months in the mitral group. The risk of bleeding (92.2+/-3.8% at 12 and 24 months in the aortic group; 85.5+/-6.0% in the mitral group) illustrated the risk of mechanical valve implantation in an elderly population.