This study was performed to evaluate the acute oral toxicity of an oriental medical prescription for obesity treatment, SH21-B, in Sprague-Dawley rats and Beagle dogs. SH21-B was administered in rats at does of 0mg/kg, 2,000mg/kg, and 5,000mg/kg. And also SH21-B was administered in Beagle dogs at does of 150mg/kg, 300mg/kg, and 600mg/kg. The rats and dogs of both sexes were observed daily for 14 days after single oral administration. Two female rats, one administered at 2,000mg/kg and the other administered at 5,000mg/kg, died, but no dead animal was observed among male rats. Therefore LD50 in the female rat is observed to be 8,710mg/kg, and MLD(Minimum Lethal Dose) of the male rat is observed to be more than 5,000mg/kg. Among dogs, no dead animal was observed up to 600mg/kg and MLD is observed to be more than 600mg/kg.