Three patients with advanced Graves' ophthalmopathy were treated with cyclophosphamide. All had proptosis and diplopia. One patient had disabling iatrogenic Cushing's syndrome from steroid treatment of the ophthalmopathy and had undergone bilateral orbital decompression before cyclophosphamide therapy; steroids could not subsequently be withdrawn. When cyclophosphamide was administered to the cushingoid patient, withdrawal of glucocorticoid therapy was then possible. Diplopia completely resolved in two patients and improved in the third coincident with administration of cyclophosphamide. Deteriorating visual acuity resolved in one patient. Chemosis improved in the two affected patients. Proptosis was unchanged in all three patients. Cyclophosphamide deserves further study as a therapeutic agent in Graves' disease.