BACKGROUND Although some cases of hepatocellular carcinoma (HCC) are known to possess a sarcomatous appearance, their cytologic characteristics in ascites have not been reported. METHODS Two Japanese males, aged 67 and 60 were admitted to the Gifu Municipal Hospital because of liver tumors. In the first case, although transcatheter arterial embolization (TAE) was performed, ascites with neoplastic cells continued to enlarge, and the patient died of liver failure. In the second case, although TAE, percutaneous ethanol injection therapy, chemotherapy and radiotherapy were performed, the patient died of tumor progression: expansion of the hepatic tumor, metastases to distal organs and increasing malignant ascites. Neoplastic cells in the ascites of both cases had nuclei that were shaped irregularly or were vesicular and contained conspicuous nucleoli. A number of multinucleated giant cells were also seen. Immunocytochemically, numerous neoplastic cells were positive for alpha-fetoprotein. These findings suggested sarcomatous HCC. Also, histologic findings of the liver tumors at autopsy showed the appearance of sarcomatous HCC. CONCLUSIONS In both cases presented, HCC cells with sarcomatous change were observed in ascites. To our knowledge, this is the first report describing the cytologic diagnosis of sarcomatous HCC in ascites.