We present the first case report of an olfactory neuroblastoma (esthesioneuroblastoma) diagnosed by cytologic examination. The patient was a 40-year-old male who had a 13-year history of "adenocarcinoma" of the nasal cavity until the correct diagnosis of olfactory neuroblastoma was made cytologically from pleural fluid shortly before his death. The cells had the typical features of rosette formation, scanty elongated cytoplasm, clustering of cells and nuclear compression resulting in an "onion-skin" appearance. Surgical specimens, several biopsies and fine needle aspiration of a metastatic deposit in a lymph node all showed, retrospectively, features of esthesioneuroblastoma. Electron microscopy showed membrane-bound dense-core secretory granules. Autopsy findings revealed multiple metastases but no tumor at the original site; that tumor had been treated with high-dose radiation therapy as well as systemic chemotherapy. Olfactory neuroblastoma is a rare tumor, but it is important to recognize because it has a better prognosis than the more commonly encountered malignancies of the nose.