The present study investigated the antiproliferative effects of Crnum asiaticum var. japonicum against HL-60 human leukemia cells. The 80% MeOH extract or several solvent fractions from the C. asiaticum inhibited the growth of HL-60 cells, whereas the growth of HEL-299 cells, human embryonic lung fibroblast, was scarcely inhibited. When the HL-60 cells were treated with the $CHCl_3$ fraction, the BuOH fraction, the EtOAc fraction and the $H_2O$ fraction, DNA ladder, chromatin condensation and increase of sub-G1 hypodiploid cells were observed. Furthermore, the $CHCl_3$ fraction and the BuOH fraction reduced Bc1-2 mRNA level, whereas Bax mRNA level was increased. These results suggest that the inhibitory effect of C. asiaticum on the growth of the HL-60 cell might be mediated through the induction of apoptosis via the down-regulation of Bc1-2. Taken together, components of C. asiaticum might have a therapeutic potential for the treatment of human leukemia.