Abstract: OBJECTIVE To investigate the effects of N-acetylcysteine (NAC) injection on tetrachloride (CCl4)-induced injury in primary rat hepatic cells. METHODS Primary cultured hepatic cells were induced injury by CCl4. The cells were incubated with NAC(100, 20, 4 μmol·L^-1) for 20 h. The expressions of aspartate transaminase(AST) in hepatic cells were determined by MTT assay. RESULTS After incubated with NAC for 20 hours, neither viability of primary rat hepatic cells decreases significantly, nor released AST from hepatic cells increases significantly in medium. However, in 4-100 μmol·L^-1, NAC reversed concentration-dependently the CCl4-decreased viability, and the EC50 was about 20 μmol·L^-1; in 100 μmol·L^-1, NAC inhibited effectively CCl4-increased AST in primary rat hepatic cells, and attenuated obviously the change of hepatic cell morphous. CONCLUSION NAC has a protective effect on tetrachloride-induced injury.