A case of metastatic adenoid cystic carcinoma of the lung, originated from the trachea, was diagnosed by fine needle aspiration. Although the cytologic features of adenoid cystic carcinoma have been well described, it is easy to confuse adenoid cystic carcinoma with more common primary small cell neoplasms of the lung, i.e., small cell carcinoma, well differentiated adenocarcinoma, and carcinoid tumor of the lung. The features distinguishing adenoid cystic carcinoma from these neoplasms include 1) tight, globular, honeycomb pattern of cells, 2) acellualr basement membrane material in the lumen, and 3) cells lacking true nuclear melding and having bland chromatin pattern. The morphologic feature of metastatic adenoid cystic carcinoma in this case was so distinctive as to permit a definite diagnosis by aspiration cytology.