We investigated the effects of tauroursodeoxycholate (UR-906) and ursodeoxycholic acid (UDCA) on alpha-naphthylisothiocyanate (ANIT)-induced cholestasis in mice. UR-906 and UDCA were given intravenously 2 hr prior to and 2 hr after ANIT (80 mg/kg, p.o.) treatment. The animals were sacrificed 48 hr after ANIT administration, and serum markers of liver injury were examined. UR-906 prevented significant elevations in total bilirubin, bile acids and LDH. Furthermore, this drug reduced significant elevations in ALP and LAP. UDCA also prevented significant elevations in total bilirubin and LAP. These results indicate that UR-906 as well as UDCA has a beneficial effect against ANIT-induced cholestasis in mice.