The antiproliferation effects and inhibition of telomerase activity of oridonin on leukemic HL-60 cells were studied. HL-60 cells in culture medium were treated with different concentrations of oridonin. The inhibitory rate of the cells was measured by MTT assay. Cell apoptotic rate was detected by flow cytometry (FCM). Morphology of cell apoptosis was observed by Wright's stain. Reverse transcriptase polymerase chain reaction (RT-PCR) and PCR-enzyme-linked immunosorbent assay (ELISA) were used to detect hTERT mRNA expression and telomerase activity before and after apoptosis. Oridonin (over 8 micromol/l) could inhibit the growth of HL-60 cells and cause apoptosis significantly. The suppression was in both time-dependent and dose-dependent manner. Marked morphological changes of cell apoptosis including condensation of chromatin and nuclear fragmentation were observed clearly by Wright's stain especially after the cells were treated 48-60 h by oridonin. The expression of hTERT mRNA as well as activity of telomerase were decreased concurrently by treatment with oridonin in HL-60 cells. Oridonin can downregulate the hTERT mRNA expression and decrease the telomerase activity of HL-60 cells; it has apparent antiproliferation and apoptosis-inducing effects on HL-60 cells in vitro.