The bioflavonoid quercetin, a polyphenolic compound widely distributed in the plant kingdom, is known to its antioxidative, antitumour, immunomodulative, and anti-inflamatory properties. It also has been shown to act as a hyperthermia sensitizer by increasing the apoptosis in a variety of tumour cell lines both in vitro and in vivo. The aim of this study was to explore and compare antitumour, genotoxic and immunomodulatory effects of cytostatic cisplatin and/or immunomodulator quercetin with and without hyperthermia in mice-bearing Ehrlich ascites tumour (EAT) using the method of alkaline comet assay. In Swiss albino mice preventively treated intraperitoneally (i.p.) by quercetin (50 mg kg-1) on the 7th and 3rd day before i.p. injection of 2x106 EAT cells. Chemotherapy (37°C) and hypothermical chemotherapy (43°C) with cisplatin (5 or 10 mg kg-1) were given on the 3rd day after the tumour cell injection into the abdominal cavity of mice. These results of alkaline comet assay suggest the synergistic effect of hyperthermia, chemotherapy and immunotherapy with quercetin in increased DNA protection of leukocytes, hepatocytes and kidney cells from damages caused by toxic metabolites of cispaltin. It is likely that immunomodulation of quercetin and reducing toxicity of chemotherapy treatment with quercetin may be possible mechanism of antitumour efficiency. The analisys of the results has led us to the conclusion that the combination of quercetin with cytostatic cisplatin could increase the antitumour potential of chemoterapeutic agents which suggests the benefits of potential clinical use in order to maximize immunity of organism and minimize harmful effects of toxic metabolites of cytostatic cisplatin on normal cells and tissues.