Objectives : This study was focused to investigate the toxicity of Saussurea lappa (SL) extracts in HL-60 cells and human lymphocytes. We also examined the differentiation effect of SL against leukemia cells. Methods : For examining the toxicity of SL, cytokinesis-block micronucleus (CBMN) assay and single cell gel eletrophoresis (SCGE) assay were used in present study. The cell differentiation effect of SL was evaluated by nitroblue tetrazolium (NBT) reduction assay. Results : The inhibition of cell growth in HL-60 cells was observed in a dose-dependant manner after SL treatment for 24 h. According to SCGE assay, HL-60 cells treated with SL increased DNA damage at $10{mu}g/m{ell}$, while DNA damage was induced by 0.1, 1, $10{mu}g/m{ell}$ concentration of SL in human lymphocytes. Our results indicated that SL have no genotoxic effect in HL-60 cells and human lymphocytes. Additionally, the differentiation effect was induced in $1{mu}g/m{ell}$ SL-treated HL-60 cells. Conclusions : From above results it is suggested that SL could be beneficial for the preparation of the useful agent for treating leukemia.