Extreme confusion exists in the correct differentiation of the different vascular disturbances of the extremities. This is due largely to failure to make the fundamental distinction between the functional or vasomotor, and the organic or obliterative lesions. Careful investigation of all the palpable arteries is the sine qua non of the differential diagnosis. This allows the primary differentiation in more than ninety per cent. of the cases. The circulatory efficiency test is also of great value in making the decision as to the functional or occlusive nature of the disorder. Many cases of thrombo-angiitis obliterans and arteriosclerotic disease present vasospastic disturbances with color changes in the hands and feet; this leads to erroneous diagnosis. Early recognition of thrombo-angiitis obliterans is of great importance, as gangrene is frequently prevented. Meddlesome surgery of the toes was the irritating factor in producing gangrene in fifty per cent. of our cases. Minor surgical measures on the feet of elderly persons, particularly men, must not be undertaken without the condition of the arteries first having been determined. Cognizance of this fact will prevent gangrene in a definite percentage of cases of arteriosclerotic disease.