VEGF and TGF-β1 are cytokines that stimulate tissue invasion and angiogenesis. These factors are considered as molecular targets for the therapy of glioblastoma. Bevacizumab, a recombinant humanized monoclonal antibody developed against VEGF, inhibits endothelial cell proliferation and vessel formation. Flavonoids obtained from Dimorphandra mollis and Croton betulaster have been described as proliferation inhibitors of a human glioblastoma derived cell line. VEGF and TGF-β1 levels were dosed by ELISA in a GL-15 cell line treated with bevacizumab and also with the flavonoids rutin, 5-hydroxy-7,4′-dimethoxyflavone, casticin, apigenin and penduletin. Rutin reduced the VEGF and TGF-β1 levels after 24 h but not after 72 h. The other flavonoids significantly reduced TGF-β1 production. Bevacizumab reduced only the VEGF levels in the supernatant from GL-15 cultures. These results suggest that the flavonoids studied, and commonly used in popular medicine, present an interesting subject of study due to their potential effect as angiogenic factor inhibitors. Copyright © 2010 John Wiley & Sons, Ltd.