In an effort to decrease the incidence of thromboembolic phenomena associated with prosthetic replacement of the mitral valve and to eliminate problems associated with swelling of moving parts employed in cardiac valve prostheses, a new mitral Teflon disc valve made of titanium was designed. The cage legs are covered with Teflon to reduce wear, and the entire sewing ring and base are covered with Dacron velour to encourage rapid tissue encapsulation. After accelerated fatigue testing and animal investigations, preliminary results in a clinical series of 73 patients appear most encouraging. Further time must pass, however, before statistically valid conclusions can be reached.