Abstract: Objective To observe the effect of sodium arsenite(NaAsO₂)exposure on human melanoma cell lines of G361 and A375,and to explore whether there were differences between the effects of apoptosis induced by these two cell lines.Methods Cells were exposed to NaAsO₂ of 0,1,5,10,20 and 40 μmol/L,and actinomycin of 5 μg/μl,then collected after being cultured for 24 h.10000 cells were measured for apoptosis and necrosis rates.Results Apoptosis rate of 20 and 40 μmol/L NaAsO₂ groups were significantly higher than that of control in both G361 and A375;Necrosis rate of 40μmol/L NaAsO₂ group in G361 and 20,40μmol/L NaAsO₂ groups in A375 were markedly higher than that of control;apoptosis rate of A375 induced by NaAsO₂ exposure of 20,40 μmol/L and actinomycin of 5 μg/μl were significantly lower than those of G361.Conclusion NaAsO₂ exposure can induce apoptosis in human melanoma cell line.The effect of apoptosis induced by NaAsO₂ is different in different cell lines of human melanoma.