Malignant neoplasms arising in the nasal fossa are uncommon; they are estimated to comprise about 2 per cent of all malignant disease in the United States (7). If nasal polyps are excluded, 3 per cent of the nasal tumors are of neurogenic origin (26). Among these are gliomas, neurofibromas, ganglioneuromas, meningiomas, neurilemmomas, and esthesioneuro-epitheliomas. Esthesioneuroepithelioma, a malignant neoplasm of the olfactory apparatus, is composed of undifferentiated neuroectodermal tissue. This tumor, with a histologic pattern similar to that observed in tumors of the sympathetic ganglia, the adrenal medulla, and the retina, is also referred to as olfactory neuroblastoma, esthesioneuroblastoma, and esthesioneurocytoma. Since the neoplasm has an anaplastic appearance, it has been mistaken for undifferentiated epidermoid carcinoma, myxosarcoma, undifferentiated adenocarcinoma, reticulum-cell sarcoma, lymphosarcoma, malignant melanoma, plasmacytoma, and some vascular neoplasms. The difficulty in making the diagnosis of esthesioneuroepithelioma is illustrated in a series of 8 cases reported from the Mayo Clinic in a review of 504 intranasal neoplasms. The diagnosis was made retrospectively in 4, and in 2 others it had been in doubt (29). In 1924 Berger, Luc, and Richard (4) described an olfactory nerve tumor which resembled a retinoblastoma histologically. They called it esthesioneuroepithelioma. Two years later, Berger and Coutard (3) described a second intranasal neurogenic tumor differing somewhat in histologic pattern and termed it esthesioneurocytoma. Seaman (37) and Schall and Lineback (36) first reported this tumor in the American literature in 1951. Case Reports Case I (F. A.): On April 22, 1957, a 32-year-old white man was admitted to the Columbia-Presbyterian Medical Center with a history of right nasal obstruction of six months duration. Some pain was present, but no epistaxis or purulent rhinorrhea. On physical examination right nasal obstruction was found, with hypertrophy and distortion of the middle turbinate. Radiographic examination of the paranasal sinuses disclosed a diffusely clouded right antrum. On April 23 a right Caldwell-Luc procedure was performed. The entire right antrum was found to be filled with a large cystic mass, apparently quite firm and attached to the superior wall. This was excised in large pieces and the remaining mucous membrane was then removed by curettement. A large polypoid portion of the middle turbinate was resected with a snare. All tissues submitted for pathology had the same microscopic appearance (Fig. 1). The diagnosis was esthesioneuroepithe-lioma of the right maxillary sinus and right middle turbinate. The sections disclosed that total excision had not been accomplished. The patient was observed until Nov. 27 when a recurrence, a soft reddish polypoid mass, was found on the right middle turbinate.