To study the effects of Scorpio on oxygen free radical-mediated damage by xanthine oxidase/hypoxanthine (XO/HX) on cultured spinal sensory neurons, in vitro assays such as MTT assay were used in cultured spinal sensory neurons derived from mice. Spinal sensory neurons were cultured in media containing various concentrations of XO/HX for 6 hours, after which the neurotoxic effect of XO/HX was measured by in vitro assay. The protective effect of the herb extract, Scorpio water extract against XO/HX-induced neurotoxicity was also examined. The results are as follows : In MTT assay, XO/HX significantly decreased the cell viability of cultured mouse spinal sensory neurons according to exposure concentration and time in these cultures. The effect of Scorpio water extract on XO/HX-induced neurotoxicity showed a quantitative increase in neurdfilament. These results suggest that XO/HX has a neurotoxic effect on cultured spinal sensory neurons from mice and that the herb extract, Scorpio water extract, was very effective in protecting XO/HX-induced neurotoxicity.