In this study the effects of epirubucin (EPI), an antineoplastic drug, on cell proliferation, labelling index and mitotic index of Ehrlich ascites carcinoma (EAC) cells under in vivo and in vitro conditions were investigated. In the in vitro study, epirubicin was applied to EAC cells in doses of I mug/mL, 2 mug/mL, 4 mug/mL and 6 mug/mL. In the in vivo study, EPI 0.02 mg/g and EPI 0.04 mg/g were injected to mice intraperitoneally. These doses, applied both in vivo and in vitro studies, inhibited the proliferation of EAC cells as well as DNA synthesis and mitosis. It was found that this effect depended on increased amount of drug applied and time.