The success of conservative therapy in thrombo-angiitis obliterans is dependent on the recognition of this malady in its early stages. With the various diagnostic methods available today there should be comparatively little difficulty in determining the presence of arterial occlusion in the extremities long before the terminal stage of gangrene has developed. If this conception is sufficiently emphasized, the term "presenile gangrene" as a disease entity should soon disappear from the confused terminology of peripheral vascular disease. It is my purpose in this communication to focus the physician's attention not on the gangrene, which is only rarely encountered, but on the underlying pathologic process, which is, in every case of thrombo-angiitis obliterans, an arterial occlusion of varying extent. As Silbert and I1have shown, the prognosis under proper therapy is most encouraging when the arterial obstruction, as measured with the oscillometer,2has not progressed to any great degree.