The aim of this study was to investigate the protective activity of curcumin, demethoxycurcumin and bisdemethoxycurcumin, isolated from Curcuma longa Linne, on hepatocyte injury induced by carbon tetrachloride (CCl$_4$,10 mM), t-butyl hydroperoxide (TBH, 0.5 mM) and D-galactosamine (GaIN,30 mM). Primary cultures of rat hepatocyte (18 h culture) were treated with CCl$_4$, TBH or GaIN and various concentrations (0.1, 1, 10 and 100 ${mu}$M) of curcumin, demethoxycurcumin and bisdemethoxycurcumin CCl$_4$ significantly increased the levels of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The increases in LDH, ALT and AST levels were inhibited by curcumin. Demethoxycurcumin and bisdemethoxycurcumin decreased the levels of AST. Curcumin inhibited the increases in ALT and AST levels induced by TBH. The increased levels of LDH, ALT and AST induced by TBH were inhibited by bisdemethoxycurcumin. GaIN markedly increased the levels of LDH, ALT and AST. These increases were significantly inhibited by bisdemethoxycurcumin. The increase in AST level was inhibited by curcumin. These results suggest that curcumin and bisdemethoxycurcumin have potent hepatoprotective activities.