Objective To investigate the effect of saw palmetto extract (SR) on GL261 glioma in rats and immune system.Methods The 40 rats were divided into 4 groups randomly,one was the control group without tumor (n =10),the other 30 rats were given subcutaneous inoculation of tumor cells and then divided into 3 groups:tumor-bearing group (n =10),low dose SR group (n =10),and high dose SR group (n =10).After 1 weeks feeded,the rats of SR groups were given the saw palmetto extract,low dose group 50 mg/kg once a day every other day and 300 mg/kg of high dose group every other day.The tumor-bearing groups received the same dose of distilled water.After 4 weeks feeding,we measured the tumor weight and the inhibition rate was calculated.The tumor cell apoptosis was detected by TdT mediated dUTP nick-end labeling (TUNEL) staining.The splenic T lymphocyte proliferation was tested by methyl thiazolyl tetrazolium (MTF).Results (1) The SR groups compared to tumor group,the tumor weight was significantly reduced (F =62.678,P =0.000).The tumor inhibition rate was significantly higher in high dose group.(2) The apoptosis of tumor cells in tumor-bearing group was significantly less than SR groups and the apoptosis was significantly increased after treatment with SR,especially in high dose SR group (F =1.287E3,P =0.000).(3) Compared to SR groups and control group,T lymphocyte proliferation of tumor-bearing group reduced obviously.After treated with SR,T lymphocyte proliferation significantly increased and was higher in high-dose group (F =103.565,P =0.000).Conclusions Saw palmetto extract can activate T lymphocytes and induce apoptosis to tumor cells.Its function was related to SR concentration.