Abstract: Objective To investigate the effects of genistein on the growth and cell cycle of human glioma cell line U251MG.Methods The growth inhibition of U251MG cells was measured with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenytetrazolium bromide(MTT)assay.Phase distribution of cell cycle was analyzed with flow cytometry.The expression of cyclin B1 and cyclin-dependent protein kinase 1(CDK1)were determined with western blotting.Results Genistein inhibited the grow th of U251MG cells significantly in a dose-and time-dependent manner.When U251MG cells were treated with genistein for 48 hours,the cell cycle was arrested in the G2₂/M phase and cyclin B1,CDK1 protein expressions were significantly decreased in a dose-dependent manner(P<0.01,P<0.01).Conclusion Genistein can inhibit the grow th of U251MG cells significantly.G2₂/M arrest of U251MG cells after treated with genistein may be related to the decreased protein expression of cyclin B1 and CDK1.