In the course of anthracyclin administration, melatonin acts as an effective scavenger of oxygen free radicals and exerts cardio- and nephroprotective effects. The present study aimed at corroborating cytostatic effectiveness of daunorubicin, applied in parallel with melatonin, in rats with transplanted Morris hepatoma. The percentage of tumour cells, which manifested traits of necrosis was recorded and extent of apoptosis was evaluated in tumour cells and in cells of myocardium. Daunorubicin administration was followed by a significant increase in necrosis and apoptosis in tumour cells and by intensified apoptosis in myocardium cells. Melatonin administered in parallel with daunorubicin decreased the extent of necrosis in tumour cells and reduced the proportion of apoptotic cardiomyocytes.