A 44-yr-old woman with a long-standing history of painful mandibular swelling was hospitalized for the diagnostic evaluation of an osteolytic mandibular lesion in the premolar-canine area. Fine-needle aspiration biopsy (FNAB) was performed and cytologic smears were characterized by clusters, sheets, and rare isolated pleomorphic cells of the squamoid type, blocks of amorphous material encircled by fibroblasts, and occasional calcifications. A cytological diagnosis of Pindborg's tumor was made, which was confirmed by histopathological examination. Evaluation of DNA ploidy by semiautomated image cytometry produced an aneuploid histogram. The patient is free of residual neoplasm at a 12-mo post-operative interval. The cytological differential diagnosis of this rare odontogenic neoplasm is discussed briefly.