Reports of tumors of the glomus jugulare have increased in recent years and there are now well over 300 recorded cases. The neoplasm has become interesting to radiologists because of both diagnostic and therapeutic considerations. Collaboration with otologists and neurosurgeons has increased the number of cases diagnosed early and has decreased the morbidity and mortality. The tumors have been variously designated angiomas, hemangioendotheliomas, endotheliomas, etc. In 1941 Guild (6) described several small bodies in the adventitia of the jugular bulb for which he suggested the name “glomus jugularis” (more correctly, glomus jugulare). Similar bodies had been described many years before (1879) by Krause (10) as “tympanic glands” and had been shown by him to have an epithelioid-cell and vascular architecture similar to that of the carotid “gland.” Watzka (21) in 1932 had denied the existence of such structures, but their occurrence was confirmed by Guild in a second study (6a) in 1953, in which he stated that more than 50 per cent of these glomus formations were in the adventitia of the dome of the jugular bulb. Twenty per cent were said to be in a small osseous canal on the under-surface of the petrous portion of the temporal bone, through which the nerve of Jacobson (9th or glossopharyngeal nerve) enters the middle ear from the jugular fossa. Twenty-five per cent are found on the cochlear promontory closely related to the tympanic plexus in the middle ear, and the remainder are distributed along the nerve of Arnold (auricular branch of the vagus, or 10th cranial nerve), which traverses the temporal bone. As yet no specific function has been attributed to glomus bodies but because histologically they so closely resemble the carotid body they are believed to be chemoreceptors. Like the carotid body, they respond to a decrease in oxygen tension and to changes in the pH of the plasma and the temperature of the blood. Tumors involving them are indistinguishable from carotid body tumors. As a probable part of the chemoreceptor system of the body, the glomus jugulare is thought to be related to the adrenal medulla and similar tissues. Lattes and Waltner (11) used the terms chromaffin and nonchromaffin paraganglioma to distinguish between tissue of adrenal origin and that of the carotid type such as is found in the glomus jugulare. Capps (2) made the following differentiation: Nonc-hromaffin and Chromaffin Tissue Paragangliomas Chromaffin Tissue Paraganglioma A common embryological origin with the cells of the sympathetic ganglia. Efferent motor sympathetic innervation. Positive chromaffin reaction. Secretion of epinephrine or similar substance. Non-chromaffin Paragangliomas Direct association with cranial nerves and their ganglia and vessels of the branchial arches.