Based on previous thromboembolic complications associated with the interruption of anticoagulation during subsequent noncardiac operations in patients with nonbiological mitral prostheses, a protocol was developed for this high risk group. We report the successful management of 26 such operations in which anticoagulation was interrupted for 12 hours and then rapidly restored by means of heparin in the postoperative period. Since an earlier study suggested no adverse effect from the interruption of chronic anticoagulants for three to five days among patients with isolated aortic valve prostheses, simple interruption was again employed during 16 subsequent noncardiac operative procedures in this group with no complications. There were three episodes of hemorrhage observed in patients receiving therapeutic doses of heparin postoperatively, but only one required blood replacement.