Abstract: The effects of differentiation of human leukemia HL60 on harringtonine(Har) and camptothecin (Cam) induced apoptosis (in these cells) were studied. When treated with phorbol 12-myriate,13-acetate 16 nmol·L^-1 for 24 h,the HL60 cells differentiated into monocte/macrophage cells and were arrested at G₁ phase.The differentiated cells were shown to be resistant to the Har and Cam induced apoptosis,but showed no change of expression of c-myc gene.HL60 cells incubated in 1.4% dimethyl sulfoxide for 48 h differentiated into granulocyte cells ad were also gene arrested at G₁ phase. The differentiatde cells became resistant to the apoptosis induced by Cam,but not that by Har,and expression of c-myc decreased drasticall in the differentiated cells.The results indicatd that the differntiated status of human leukemia HL60 cells apparently affected the apoptosis induced by harringtonine and camptothecin,but it was irrelevant to the change of hte expession of c-myc gene.