The possible mechanism of the antiproliferative and apoptotic effects of Boswellia carterri water extract were studied in HL-60 human leukemia cells. The cytotoxicity of HL-60 cells after the treatment of Boswellia carterii water extract showed dose- and time-dependent manner. The apoptotic effect of 300 $mu$g/ml Boswellia carterii water extract was demonstrated by DNA laddering. The activity of caspase 3-1ike protease was markedly increased in HL-60 cells treated with Boswellia carterii water extract. Furthermore, the level of Bcl-2 was time-dependently reduced, whereas Bax protein level was enhanced by Boswellia carterii water extract treatment. In conclusion, our results suggest that apoptotic effect of Boswellia carterii water extract may partly mediated through activations of caspase-3 activity and Bax expression, and inhibition of Bcl-2 expression.