The mixed odontogenic tumors--ameloblastic fibroma, ameloblastic fibro-odontoma, and the odontomas--represent a group of lesions of which some are neoplastic and some are hamartomatous. Regarding data on age, sex distribution, and site of occurrence of the various lesions, it was concluded that the ameloblastic fibroma represents a separate entity that does not develop into a more differentiated odontogenic lesion and that the ameloblastic fibro-odontoma is an immature complex odontoma. Moreover, it was noted that the distribution according to site of the ameloblastic fibro-odontoma and complex odontoma was dependent on age, both lesions showing a more posteriorly located site of predilection with increasing age. Finally, it is supposed that age-related factors determine whether an aberrant development of the odontogenic tissues exhibits a hamartomatous or a neoplastic nature.