The ameloblastoma is by far the most common and most important odontogenic tumor. Eighty percent of ameloblastomas occur in mandible, usually in the molar ramus region. Gradual painless enlargement is the usual initial symptom. This tumors are characteristic benign in histopathologic findings, although they have a definite invasive potential manifest by a tendency to recur. The author has observed a case of ameloblastoma occurred in the left maxilla in 55-year-old man. He was treated by partial excision and biopsy followed by external radiation therapy. The patient was followed for 2 months with improvement.