The current study was performed to determine the acute oral toxicity of P55A, a crude extract of 1 : 1 mixture of Phellodendron amurense cortex and Aralia elata cortex, in SD rats and beagle dogs. 5 rats of each sex were treated with a single dose of P55A orally at doses of 0 and 5,000 mg/kg respectively. Also 2 dogs of each sex were treated with a single dose of P55A orally at doses of 0 and 2,000 mgAg, respectively. After the treatment, clinical signs, and body weight change were observed for 14 days. All rats survived during the study and did not show any clinical sign. Body weight gain showed no significant difference between the control and treated rats. Grossly, no lesion was observed in the rats. All dogs survived during the study. In clinical signs, dark stool was observed in the 2,000 mg/kg treated dogs at day 1 after administration. The animals recovered from general signs at day 2 after administration. Body weight gain showed no significant difference between the control and treated dogs. Grossly, no lesion was observed in the dogs. It is suggested that the LD$_{50}$ of P55A by oral administration was estimated to be over 5,000 mg/kg in both sexes of rats and 2,000 mg/kg in both sexes of beagle dogs.s.