Adenophora triphylla var.japonica Hara (Campanulaceae) is a perennial herb widely distributed in Korea,China and Japan.Its roots (Adenophorae Radix) have been used as an analgesic,an anti-inflammatory and an antitussive in oriental medicine.Further investigation of the pharmacological effects shows that this plant has anti-obesity,anti-cholesterolemia,anti-hyperglycemia,anti-gastric cancer,anti-bacteria,and anti-inflammatory activities etc.It has been reported that Adenophorae Radix contains five alkaloids,[1] two triterpenoids,two phytosterols,lupenone,[2] polysthicol and saponins.In the present study the effect ofA.triphylla var.japonica roots was first studied on acetaminophen-induced liver injury.The extracts exhibited the hepatoprotective properties against acetaminophen-induced hepatotoxicity.AST (aspartate aminotransferase),ALT (alanine aminotransferase) and LDH (lactate dehyderogenase) activities were significantly inhibited by pre-treatment or post-treatment of the extracts compared to control in a dose-dependent manner.Post-treatment revealed better effects.Among the fractions of the total crude extracts,methylene chloride fraction inhibited more strongly than the others in a post-treatment assay.Further,the body weights of the pre-and post-treated group were increased more than that of control and the animal viability was also increased.Some components isolated from the active fraction will also be discussed.As a result,the extracts ofA.triphylla var.japonica may be clinically useful for the protection of liver damage.