A 60-year-old woman, who had undergone curettage of a mandibular ameloblastoma about 20 years before, presented with recurrence of an ameloblastoma in the mandibular symphysis. This tumor was removed by a marginal resection. About 2 years later, the tumor recurred in the right mandibular ramus, and the patient underwent right mandibulectomy. About 6 months later, the tumor again recurred. Radical resection was performed, but invasion of the infraorbital region and cranial base was noted. An anterior craniotomy was then performed and the lesion removed. Histologically, proliferation of squamous cells associated with atypia was seen, and ameloblastic features were no longer observed. Metastasis to the lung was noted 1 year later.