Aucubin, an iridoid glucoside which was previously reported to exhibit liver-protective activities against $CCl_4$ and ${alpha}-amanitin$ induced liver damages, was subject to toxicological studies. To measure the lethal dose, the doses of 100mg/kg, 300mg/kg, 600mg/kg and 900mg/kg were administered intraperitoneally to experimental mice. No death was observed 24 hrs later, but serum GOT and alkaline phosphatase activities were deceased slightly at the doses of 300mg to 900mg/kg, and the triglyceride contents were slightly increased. To investigate acute toxicity of aucubin itself, multiple dosages(20 mg/kg, 40 mg/kg and 80 mg/kg for four times a week) were injected intraperitoneally into mice, then serum enzymes activities and chemistries were assayed; no significant change of the enzyme activities of alkaline phosphatase, GPT, GOT in the test groups were observed in comparison with those of the control group, and the contents of triglyceride, glucose, urea nitrogen and total proteins in the test group serums appeared to be almost same levels as those of the control group were. Histological examiation on liver biopsy samples indicated no gross changes between the control group and the test group were noted. Therefore, aucubin appears to be apparently low toxic substance and its minimum lethal dose in mouse seems to be more than 0.9 g.