Carotid body tumors are encounterd infrequently. During the past 30 years, 15 patients with 16 carotid body tumors have been treated at our medical center. All patients have been followed for a minimum of 7 years. The major findings relate to the areas of greatest controversy concerning carotid body tumor treatment: the need for excision, the value of preoperative arteriography, the role of radiation therapy, the criteria of malignancy, and the indications for and technique of carotid artery replacement. Discussed at length are our conclusions that (1) arteriography is absolutely diagnostic and therefore mandatory when carotid body tumor is suspected; (2) radiation therapy has little if any value and has increased the difficulty of excision; and (3) all carotid body tumors should be considered to be malignant. The familial tendency of this tumor is explored in relation to this last conclusion, and we report what we believe is the first finding of both a "benign" and "malignant" tumor occurring in the same family. The techniques of subadventitial excision and carotid artery replacement with autogenous saphenous vein, the latter necessary on three occasions, are demonstrated. There were no operative deaths, no serious complications after operation, and no recurrence or metastasis following total excision. However, two patients died as a direct result of tumor growth following biopsy without excision.