A preliminary study was undertaken to assess the feasibility and the diagnostic role of fine-needle aspiration cytology (FNAC) in the preoperative evaluation of eight uterine smooth muscle tumors manifesting as single large masses with signs of growth. Percutaneous FNAC was performed under echographic control with a 22-gauge needle and the material was stained according to conventional techniques. Histology of surgically resected specimens was available for final diagnosis and comparative analysis in all the cases, including five leiomyomas (LM), one smooth muscle tumor of uncertain malignant potential (TUMP), and two low-grade leiomyosarcomas (LMS). Cellularity, as indicated by the density (crowding) of nuclei reflecting the amount of cytoplasmic volume, and the cohesiveness of the tissue fragments in the smears appeared to be the most important diagnostic parameters in the distinction between LM and LMS. LM usually showed few scattered poorly cellular fragments of highly cohesive tapering cells without nuclear crowding and with abundant cytoplasm. LMS usually showed a large number of single cells and fragments of loosely arranged tapering cells with nuclear enlargement and crowding and ill-defined scanty cytoplasm. Borderline forms such as TUMP were hardly distinguishable from LMS and LM. FNAC appears to be a feasible preoperative procedure in uterine smooth muscle tumors and may play a diagnostic role, especially in distinguishing frankly benign from overtly malignant forms.