This report deals with our experience with totally cloth-covered prostheses over a 28-month period from April, 1967 to August, 1969. During this interval 223 patients were treated with an operative mortality of 11%. The earliest model cloth-covered prosthesis proved in some instances to have an excessively large transprosthetic gradient. 8,9 The introduction of the composite seat design, however, has resulted in a prosthesis with very favorable hydraulic characteristics, as shown by late postoperative catheterization studies. Early follow-up data indicate that the composite seat style prostheses have a favorably low rate of thromboembolic complications. In 88 patients receiving this style valve, there have been no early emboli and only one late embolus, despite the fact that a portion of the group are not taking anticoagulants. We stress, however, that these still represent short-term observations and must stand the test of time. Until the results of the double-blind study are completed, we continue to recommend long-term anticoagulation for all patients in whom this can be safely done. The composite seat style totally cloth-covered prosthesis is recommended for all patients who are reoperated for ball variance. We also feel it should be considered strongly for young persons undergoing aortic valve replacement and for patients who for medical or social reasons cannot be safely anticoagulated.