The effects of cyclophosphamide (Cy) on the clearance of IgG-sensitized erythrocytes (EA) were examined. The results clearly indicate that Cy treatment enhances the capacity of the mononuclear phagocytic system to remove antibody-coated cells from the circulation in normal and decomplemented mice. The enhanced rate of clearance is the consequence of an increased uptake of EA by the liver and spleen. We explored the possibility that the enhancement of Fc receptor-mediated clearance might be an important effect to be taken into account in the search for a more effective therapy of immune complexes diseases.