OBJECTIVE To validate the anticancer effect of Angong Niuhuang pill (AGNH) and pinpoint associated molecular mechanisms using human cancer cells.METHODS Human MGC-803 gastric carcinoma and human BEL-7402 hepatocarcinoma cells were incubated with AGNH 9,30,90,300 and 900 mg·L-1 for 24,48and 72 h,respectively.Cell viability was detected with 3-(4,5-dimethylthiazol-2-yl) -5-( 3-carboxymethoxyphe-nyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and colony formation assay.Apoptosis was measured with flow cytometry and Hoechst 33258/PI staining.Change in mitochondrial membrane potential (△qψ) was detected by spectrofluorophotometer.RESULTS AGNH inhibited MGC-803 cell proliferation ( for 48 h,r =0.996,P =0.002; for72 h,r=0.756,P=0.024 ) and BEL-7402 cells (for 48 h,r =0.732,P=0.030; for72 h,r=0.702,P =0.037) in a concentration-dependent manner,as showed by MTS assay.AGNH inhibited colony formation on MGC-803 cells (r =0.914,P =0.011 ) and BEL-7402 cells (r =0.871,P =0.024) in a concentration-dependent manner for 24 h.Hoechst 33258/PI staining and flow cytometry assay showed that AGNH 900 mg·L-1 for 24 h induced apoptosis of MGC-803 and BEL-7402 cells,and the apoptosis rate was 27.2％ and 19.7％,respectively.Compared with normal control group,AGNH 900 mg·L-1 for 3 min decreased the mitochondrial membrane potential of MGC-803 and BEL-7402 cells to 15.9％ and 15.0％ of control group.CONCLUSION AGNH inhibits proliferation of human cancer cells.Apoptosis and depolarization of mitochondrial transmembrane potential are probablly its mechanism.