The aim of this study was to investigate the protective activities of daidzin, daidzein, genistein or puerarin, active isoflavonoids of Puerariae Radix, on the hepatocyte injury induced by carbon tetrachloride (CCl$_4$, 10 mM), tert-butyl hydroperoxide (TBH, 0.5 mM) and D-galactosamine (GalN, 30 mM). Primary cultures of rat hepatocytes (18 hr cultured) were treated with CCl$_4$, TBH or GalN and various concentrations (0.1, 1, 10 and 100 ${mu}$M) of daidzin, daidzein, genistein or puerarin. CCl$_4$ significantly increased the levels of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST). The increase in LDH level was attenuated by daidzein, genistein and puerarin. Puerarin also inhibited the increase in AST level induced by CCl$_4$. The increases in LDH and ALT levels induced by TBH were significantly attenuated by daidzin and genistein treatments. GalN markedly increased the levels of LDH, ALT and AST These increases were significantly attenuated by daidzein. Daidzin also inhibited the increases in LDH and AST levels induced by GalN. The increases in LDH and ALT levels were attenuated by genistein and puerarin, respectively. These results suggest that daidzin and daidzein possess hepatoprotective activities.