Objective The aim of the study was to investigate whether ethanolic extract of propolis inhibits the growth and induces apoptosis of HL-60 cells. Methods HL-60 cells were treated for 24, 48, 72 h with various concentrations ethanolic extracts of propolis(0, 50, 100, and 200 μg/m L). The proliferation of HL-60 cells was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. Subsequently, Hochest 33258 staining and terminal deoxynucleotidyl transferase d UTP nick end labeling(TUNEL) were used to test the apoptosis of HL-60 cells. We observed the expression levels of Bax and Bcl-2 in HL-60 cells by immunohistochemistry. Results MTT assay showed that various concentrations of ethanolic extract of propolis had significant inhibitory effect on HL-60 cell proliferation(P < 0.05). Typical morphologic changes could be observed by fluorescence microscope and TUNEL. By immunohistochemistry, we found the expression level of Bax was up-regulated, whereas that of Bc1-2 was down-regulated(P < 0.05). Conclusion Ethanolic extract of propolis inhibits leukemia cell proliferation and induces apoptosis in vitro. Its mechanism may be related to the regulation of Bax and Bcl-2 expression and up-regulation of Bcl-2/Bax ratio. Objective The aim of the study was to investigate whether ethanolic extract of propolis inhibits the growth and induces apoptosis of HL-60 cells. Methods HL-60 cells were treated for 24, 48, 72 h with various concentrations of ethanolic extracts of propolis (0, 50, 100, and 200 μg / mL). The proliferation of HL-60 cells was determined using the 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide (MTT) Hochest 33258 staining and terminal deoxynucleotidyl transferase d UTP nick end labeling (TUNEL) were used to test the apoptosis of HL-60 cells. We observed the expression levels of Bax and Bcl-2 in HL-60 cells by immunohistochemistry. Results MTT assay showed that various concentrations of ethanolic extract of propolis had significant inhibitory effect on HL-60 cell proliferation (P <0.05). Typical immunohistochemistry could we be observed by fluorescence microscope and TUNEL. By immunohistochemistry, we found the expression level of Bax was up-regulated , that that of Bcl-2 was down-regulated (P <0.05). Conclusion Ethanolic extract of propolis inhibits leukemia cell proliferation and induces apoptosis in vitro. Its mechanism may be related to the regulation of Bax and Bcl-2 expression and up-regulation of Bcl -2 / Bax ratio.