Arabinoxylan extracted from Vietnamese rice bran was examined for its effect on murine lymphocyte activity. The mice were administered orally at four different doses: 50, 75, 100, 200 mg/kg/day for 30 days. The highest secretion of INF-y in mouse serum was 340 pg/ml at 200 mgl kg/day dosage. However, the maxium increasing rate in mortality of Sarcoma 180 cell line was 1833 percent at a dose of 100 mg/kg/day, in comparison to the control. Thus, Arabinoxylan from Vietnamese rice bran acts as a potential immunomodulator to stimulate the immune system through stimulating the natural killer cell activity and secretion of INF-y.