The present investigation was undertaken to obtain hemodynamic data from 5 patients who did not have bone cement inserted at operation and 5 patients who did. Patients in Group I, without bone cement, had no significant hemodynamic change after release of the tourniquet, whereas patients of Group II, in whose operations bone cement was used, had pulmonary and systemic hemodynamic changes. Total knee replacement with the use of bone cement to fix the prosthesis induces an immediate, important pulmonary vascular obstruction and decrease in left ventricular performance after release of the tourniquet. Such hemodynamic changes may explain the cardiac arrest previously reported, particularly when intravascular volume expansion is inadequate to correct the hypovolemia and the increase in right ventricular afterload induced by the release of the tourniquet.