A 47-year-old male smoker with chronic eosinophilia developed progressive ischemia in his extremities. Pathologic examination of vessels in amputated limbs revealed changes of thromboangiitis obliterans. Focal segments of some arteries, however, revealed infiltration of thrombus and vessel wall by eosinophils. Furthermore, the patient developed a totally occluded right temporal artery, which on biopsy specimen showed marked infiltration by eosinophils within the vessel wall. In contrast to most patients with the hypereosinophilic syndrome, however, this patient had no evidence of endomyocardial thrombosis or fibrosis. In view of recent evidence that eosinophil granule proteins are toxic to endothelial cells, the findings in this patient suggest the possibility that eosinophils may be involved in the pathogenesis of thromboangiitis obliterans.