A clinicopathological study was made in ninety-four cases in which extremities were amputated at the Mayo Clinic for occlusive vascular disease; forty amputations were through the thigh and fifty-four were below the knee.

Dissection and microscopic examination of the forty limbs amputated above the knee demonstrated the segmental nature of the occlusive arterial lesions in atherosclerosis obliterans. Limbs amputated above the knee that contained fresh thrombi in the femoral or popliteal arteries were clinically the most ischaemic of the entire series of ninety-four limbs examined.

Patients with diabetes mellitus who were subjected to amputation above the knee did not have fresh thrombi in the popliteal or femoral arteries. This correlates with the clinical finding that recent sudden arterial occlusion is relatively infrequent as the initiating factor for amputatiomi in patients with both atherosclerosis and diabetes.

The anterior tibial, posterior tibial, and peroneal arteries of limbs amputated for atherosclerosis obliteramis showed no quantitative differences in the degree of occlusion in those amputated above the knee compared with those amputated below the knee.

The old lesions of thromboangiitis obliterans may bear a strong histological resemblance to certain other thrombotic lesions, such as those secondary to emboli. The microscopic picture of thromboangiitis obliterans is not always specific and its diagnosis requires that the pathologist be familiar with the clinical history and findings in all cases.