A retrospective analysis of 72 cases of primary malignant tumors of the parotid gland treated at the University of Illinois Hospital, Chicago, from 1950 through 1978 revealed that six of these had developed from two to 24 years after irradiation of the head or neck for various benign and malignant neoplastic conditions. At the time of irradiation, ages ranged from 7 to 73 years; the sex distribution was equal. From our findings and those in 26 cases reported by various other authors, the following criteria are proposed for the designation of a parotid tumor as being radiation induced: (1) well-documented radiation exposure; (20 port of irradiation must incorporate the gland in which the cancer subsequently arises; (3) exposure to a minimum of 300 rads; and (4) minimum latent period of two years. In view of the widespread use in the past of head and neck irradiation of benign neoplastic disease, the surgeon should be aware of this possible link with parotid gland tumor.