Preoperative fine-needle aspirates of 25 soft tissue tumors and four bone tumors were used for cytodiagnosis and flow cytometric DNA ploidy analysis. The results were compared with the histopathologic diagnosis and flow cytometric DNA ploidy analysis on tissue samples after surgery. There was good agreement between the cytodiagnoses and histopathologic diagnoses with regard to benign tumor or sarcoma. There was good agreement between the ploidy determinations in aspirates and tissue samples in 20 out of the 26 tumors that could be analyzed. Aneuploid cell populations were found in 13 tumors cytologically classified as sarcoma and in one tumor classified as unspecified malignant tumor. These 14 tumors also showed aneuploid cell populations in the tissue samples and were histologically diagnosed as high-grade malignant sarcomas. The combined evaluation of preoperative cytodiagnosis and DNA ploidy on aspirates may give valuable prognostic information.