The single oral toxicity of JG-381 was studied in Sprague-Dawley rats of both sexes. In this study, rats were administrated orally with dosages of 267, 400, 600, 900 and 1350 mg/kg of JG-381. We daily examined number of deaths, clinical signs, body weights and gross findings for 14 days after JG-381 administration. When we administered different doses of 267, 400, 600, 900 and 1350 mg/kg, we found 1, 4, 4, 5 and 5 male rats died and 3, 5, 4, 5 and 5 female rats died within 1 day after administration, respectively. Some clinical signs (decrease locomotor activity, salivation, soft stool, prone position, lacrimation, crouching position, convulsion, ataxic gait, incontinence of urine) were also observed during the experimental period. Our findings suggest that oral L $D_{50s}$ (95% confidence limit) for male and female rats are 327 mg/kg (270~396 mg/kg) and 250 mg/kg (256~264 mg/kg), respectively.y.