To evaluate the cytotoxic effect of oxygen radicals, xanthine oxidase(XO)/hypoxanthine(HX)-induced neurotoxicity was examined in cultured newborn mouse spinal motor neurons afterspinal motor neurons were grown in the media containing various concentrations of XO/HX.And also, the protective effect of Rhizoma gastrodiae (RG) extract against XO/HX-inducedneurotoxicity was evaluated. Cytotoxicity was measured as a cell viability adopted by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) assay. In this study, exposure ofmotor neurons to XO/HX induced cell death significantly, in a dose- and time-dependentmanners in spinal motor neuron cultures. The decrease in cell viability of motor neuronsdamaged by XO/HX was proventioned by RG extract. These results suggest that theneuroprotective effect of RG extract on XO/HX-induced neurotoxicity may result from aattenuation of oxygen radicals.