Objective: To investigate the effects of triptolide(TPL) on cell growth, cell cycle and the expressions of p21wap1/cip1 and p27kip1.Methods: MTT assay was used to determine the cell viability after triptolide treatment in human multiple myeloma RPMI-8226 cells. The effect on cell cycle distribution was determined by flow cytometry. Semi-quantitative reverse transcription-PCR was used to examine the mRNA expressions of p21wap1/cip1 and p27kip1. The protein expressions of p21 wap1/cip1 and p27kip1 were determined by West blot.Results: Triptolide of varying concentrations induced cell viability inhibition in dose- and time-related fashion and caused G0- G1 phase arrest of cell cycle progression in RPMI-8226 cells. These effects accompanied with up-modulation of the expressions of p21 wap1/cip1 and p27kip1.Conclusion: These results suggest that triptolide inhibit cell proliferation and cell cycle progression via up-regulating p21wap1/cip1 and p27kip1 and triptolide may exert its anti-cancer activity through this pathway.