Hepatoprotective sesquiterpenes were isolated from the aqueous acetone extract of Zedoariae Rhizoma, the rhizome of Curcuma zedoaria ROSCOE (Zingiberaceae). Principal sesquiterpenes, furanodiene, germacrone, curdione, neocurdione, curcumenol, isocurcumenol, aerugidiol, zedoarondiol, and curcumenone and curcumin were found to show potent protective effect on D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced acute liver injury in mice. Plausible action mechanisms for their hepatoprotective activity were clarified on the basis of the inhibitory effect on D-GalN-induced cytotoxicity in primary cultured rat hepatocytes, LPS-induced NO production in cultured mouse peritoneal macrophages, and D-GalN/tumor necrosis factor-alpha (TNF-alpha)-induced liver injury in mice.