Ameloblastomas are benign tumors derived from the odontogenic apparatus. Of these tumors, 80% originate in the mandible, while 20% originate in the maxilla. Six cases of maxillary ameloblastoma treated at the UCLA hospitals are presented; four of these cases showed extensive and destructive tumor growth involving vital structures, including the orbit, base of skull, and parasellar structures. Two of four patients with extensive disease died of their tumors, one, with extensive involvement of the base of the skull, became unavailable for follow-up, and, one year after diagnosis, one is alive with middle cranial fossa disease. A review of the medical literature provides further evidence of the locally aggressive behavior and potentially lethal nature of this tumor. No effective treatment has evolved for extensive ameloblastomas of the maxilla that have invaded surrounding vital structures. When tumor-free surgical margins are not possible, radiation therapy may offer palliation of disease.