Aims and Background: Traditional chemotherapy strategies for human leukemia commonly use drugs based on cytotoxicity to eradicate cancer cells. One predicament is that substantial damage to normal tissues is likely to occur in the course of standard treatments. Obviously, it is urgent to explore therapies that can effectively eliminate malignant cells without affecting normal cells. Our previous studies indicated that ginsenoside Rg(1) (Rg(1)), a major active pharmacological ingredient of ginseng, could delay normal hematopoietic stem cell senescence. However, whether Rg(1) can induce cancer cell senescence is still unclear. Methods: In the current study, human leukemia K562 cells were subjected to Rg(1) exposure. The optimal drug concentration and duration with K562 cells was obtained by MTT colorimetric test. Effects of Rg(1) on cell cycle were analyzed using flow cytometry and by SA-beta-Gal staining. Colony-forming ability was measured by colony-assay. Telomere lengths were assessed by Southern blotting and expression of senescence-associated proteins P21, P16 and RB by Western blotting. Ultrastructural morphology changes were observed by transmission electron microscopy. Results: K562 cells demonstrated a maximum proliferation inhibition rate with an Rg(1) concentration of 20 mu mol.L-1 for 48h, the cells exhibiting dramatic morphological alterations including an enlarged and flat cellular morphology, larger mitochondria and increased number of lysosomes. Senescence associated-beta-galactosidase (SA-beta-Gal) activity was increased. K562 cells also had decreased ability for colony formation, and shortened telomere length as well as reduction of proliferating potential and arrestin G(2)/M phase after Rg(1) interaction. The senescence associated proteins P21, P16 and RB were significantly up-regulated. Conclusion: Ginsenoside Rg(1) can induce a state of senescence in human leukemia K562 cells, which is associated with p21-Rb and p16-Rb pathways.