CHEMODECTOMA is the name proposed by Mulligan1 for that histologically similar group of tumors occurring in the carotid body, glomus jugulare, and certain other parts of the head and neck. It is now generally agreed that these tumors are not part of the chromaffin or paraganglionic systems, as used to be thought, but that they arise from both the mesoderm of the third branchial artery and the ectoderm of the glossopharyngeal nerve (Boyd).2 "Chemodectoma" connotes the special function of these cells, which is to respond to chemical changes in the blood, as related both to oxygen and carbon dioxide and to certain drugs.3 Thus the term chemodectoma is used here in preference to the older terminology, which includes both paraganglioma and nonchromaffin paraganglioma. Chemodectomas are uncommon; not more than 350 cases have been reported, although there are many articles dealing with them. The difficulty of accurate preoperative