Abstract: AIM To investigate the mechanism of apoptosis of HL60 cells induced by the annonaceous acetogenin, squamocin. METHODS Induction of apoptosis was determined through Hoechst33258 dye staining and DNA agarose gel electrophoresis. Expression of the proteins was detected using Western blot analysis. Caspase-3 activity was detected using caspase-3 kit. RESULTS Treatment of HL-60 cells with squamocin resulted in extensive nuclear condensation, DNA fragmentation, cleavage of the death substrate poly(ADP-ribose) polymerase (PARP) and induction of caspase-3 activity. Pretreatment of HL-60 cells with caspase-3 specific inhibitor DEVD-CHO prevented squamocin induced DNA fragmentation, PARP cleavage and cell death. Stress activated protein kinase (SAPK/JNK) was activated after treatment with squamocin in HL-60 cells. CONCLUSION These results suggest that apoptosis of HL-60 cells induced by squamocin require caspase-3 activation, and could be related to SAPK activation.