Buerger's disease (thromboangiitis obliterans or TAO) is a clinical syndrome characterized by the development of segmental thrombotic occlusions of the medium and small arteries of the extremities. It is clinically and pathologically distinguishable from arteriosclerosis and necrotizing arteritis. Afflicted patients are mostly young, male, inveterate tobacco smokers who present with distal extremity ischemia, ischemic ulcers, or frank gangrene of the toes or fingers. Large arteries are typically spared, as are the coronary, cerebral, and visceral circulations. While mortality is not increased, patients with Buerger's disease often suffer from severe ischemic pain and tissue loss culminating in minor and major limb amputation. Clinical diagnostic criteria generally include the following: (1) history of smoking or tobacco abuse; (2) age of onset less than 45 to 50 years; (3) infrapopliteal, segmental arterial occlusions with sparing of the proximal vasculature; (4) frequent distal upper extremity arterial involvement (Raynaud's syndrome or digital ulceration); (5) superficial phlebitis; and (6) exclusion of arteriosclerosis, diabetes, true arteritis, proximal embolic source, and hypercoagulable states. Typical arteriographic patterns have been described that are suggestive, but not pathognomonic. While the cause of Buerger's disease remains unknown, the disease onset and clinical course are inextricably linked to tobacco abuse. Acute Buerger's disease is characterized histopathologically by intensely cellular vessel wall inflammation, giant cell foci, and hypercellular thrombi, but with preservation of the elastic lamina and the overall vascular wall architecture. Most investigators feel that Buerger's disease is an immune-mediated endarteritis; recent immunocytochemical studies have identified the linear deposition of immunoglobulins and complement factors along the elastic lamina. The inciting antigen has not been discovered. Tobacco abstinence generally results in disease quiescence and remains the mainstay of treatment.