The histologic characteristics of 29 nasal tumors previously diagnosed as neuroblastomas, unclassified carcinomas, or unclassified malignant neoplasms were reviewed. Electron microscopy was performed in 17. Nine tumors were neuroblastomas; six of these were classical neuroblastomas while the other three exhibited olfactory differentiation in addition to the classical neuroblastoma component. Areas of ganglioneuroblastoma were found in the metastasis of one of the three olfactory neuroblastomas. Twenty tumors were classified as neuroendocrine carcinoma because all showed a neuroendocrine pattern with remarkably uniform cells growing from benign glandular epithelium; membrane bound granules were present in the cytoplasm of cells of the ten cases in this group examined by electron microscopy. The mean age of the patients with neuroblastomas was 20 years; survival in this group was 75% at five and seven years, respectively, and 67% at ten years. Recurrences, metastasis, and death occurred within 3 years of diagnosis. There was a low percentage (25%) of multiple recurrences. The metastases were located in cervical lymph nodes, brain and spine. The mean age of the patients with neuroendocrine carcinoma was 50 years. Survival was 100% at five years, 88% at seven years, and 77% at ten years. Recurrences and metastasis in 70% of the cases occurred later than the third year. Multiple recurrences were present in 54% of the cases. The metastases affected lymph nodes, brain and spine in all cases except in one in which lungs and femur were involved. In the latter case adenocarcinoma was also present in addition to the neuroendocrine carcinoma. Three patients died, all more than five years from the time of diagnosis. No correlation was found between staging and prognosis in either group, except for Stage I disease.