To evaluate the effect of ground cherry extract on the activity of aniline hydroxylase, we gave ground cherry extract in doses of 100, 200 or 400 mg/kg i.p to mice for 1, 2 or 4 days. The aniline hydroxylase activity in the group treated with ground cherry extract increased in a dose dependant manner in all experimental groups compared with the control group, and was significantly higher in the group treated with ground cherry extract at a dose of 200 mg/kg, which also exhibited a time dependant increase over 4 days. Enzyzme kinetic analysis was performed for hepatic aniline hydroxylase activity in the group treated with 200 mg/kg for 4 days. There was no change of the Km values for aniline hydroxylase between the experimental group and the control group, but the Vmax values for aniline hydroxylase was 21% lower in the experimental group compared with the control. The experimental group also showed lower lipid peroxide and reduced glutathione content, and there were no significant difference in serum alanine aminotransferase activity between the experimental group and the control. Aniline was injected into both the experimental group mice treated with ground cherry extract at a dose of 200 mg/kg for 4 days and the control group, and then the level of blood aniline was assayed at 1hr. The level of blood aniline was lower in the experimental than the control group. This study suggests that ground cherry extract induces hepatic aniline hydroxylase activity and might accelerate the scavenging system of reactive oxygen species. It is likely that ground cherry extract influences the metabolism of xenobiotics by activating AH activity substituted for CYP2E1.