Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The flavonoid naringin is a polyphenolic compound that naturally occurs in citrus. Patients with cancer generally present features of malnutrition and cachexia. Levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) are raised in patients with cancer. This study was designed to analyze the in vivo effect of naringin in the therapeutic treatment of rats bearing Walker 256 carcinosarcoma (W256). Rats were treated intraperitoneally with different doses of naringin (10, 25 and 35 mg/kg), for 50 days. At 25 mg/kg, naringin inhibited tumor growth by similar to 75%. With this treatment, TNF-alpha and IL-6 levels decreased (p<0.05) in comparison with the control. In addition, two rats presented complete tumor regression. Inhibition of tumor growth, survival increase and the reduction of TNF-alpha and IL-6 levels in rats bearing W256 treated with naringin strongly suggest that this compound has potential as an anticarcinogenic drug.321129133Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundo de Apoio ao EnsinoPesquisa e a Extensao/UNICAMPFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)