This study was designed to investigate the effects of dibutyl phthalate (DBP) on the proliferation and apoptosis of leukemic cells. The results showed that DBP suppressed the proliferation of HL-60 and K562 leukemic cells in a dose-dependent and time-dependent manner. Inducing HL-60 and K562 leukemic cells to die via apoptosis were confirmed by that the percentage of the apoptotic cells in morphology and of the DNA fragmentation increased significantly and that typical ladders of apoptosis were shown by gel electrophoresis when HL-60 and K562 cells were exposed to the DBP. Also, K562 leukemic cells was less susceptible to the DBP than HL-60 cells. These results indicate that DBP can inhibit the proliferation of HL-60 and K562 leukemic cells and induced them to die via apoptosis.