Tumors involving the carotid sinus and glossopharyngeal nerve may produce syncope due to bradycardia and hypotension. Carotid sinus syncope unrelated to cancer is usually caused by bradycardia and responds to control of the heart rate. When neoplastic disease involves the carotid sinus, vasodepressor hypotension, with or without bradycardia, is more common. Control of the heart rate alone is not effective. Although this syndrome is not common, it is probably not recognized in milder forms. Most patients in whom this syndrome develops have cancer of the head and neck. A patient with breast carcinoma metastatic to the neck and carotid sinus is described in whom syncope with hypotension and bradycardia developed. Although a temporary cardiac pacemaker controlled bradycardia, severe hypotensive episodes recurred despite treatment with anticholinergic and sympathomimetic drugs. The pathophysiology and therapy of this syndrome in patients with cancer are reviewed.