In order to elucidate the toxic mechanism of oxygen radicals in cultured mouse spinal sensory neurons, cytotoxic effect of oxygen radicals was evaluated by M1T assay and NR assay. In addition, protective effect of Sopunghwalhyultang(SPHHT) water extract on oxidant-induced neurotoxicity was investigated on these cultures. Spinal sensory neurons derived from mice were cultured in mediums containing various concentrations of Xanthine Oxidase / Hypoxanthine(XO/HX). Cell viability was measured by MTT assay and NR assay. XO/HX-mediated oxygen radicals remarkably decreased cell viability of cultured spinal sensory neurons in a dose-and time-dependent manner. And also, SPHHT blocked XO/HX-induced neurotoxicity in these cultures. These results suggest that oxygen radicals are toxic and SPHHT are effective in blocking against the oxidant-induced neurotoxicity in cultures of spinal sensory neurons of mice.