The aim of this study was to investigate the effect of the total saponins of Panaxginseng (TSPG) on cells expression of apoptosis-related genes bax and bcl-xl in HL-60 cells and its mechanism inducing apoptosis of HL-60 cells. The morphology of HL-60 cells was observed under normal and fluorescence microscopes; the percentage of apoptotic HL-60 cells was assayed by flow cytometry and the DNA ladder was observed by DNA agarose gel electrophoresis; the expression changes of bax and bcl-xl mRNAs were detected by RT-PCR after HL-60 cells were treated with TSPG at final concentrations of 0, 100, 200, 400, 800 and 1600 microg/ml for 48 hours. The results showed that the percentage of apoptotic HL-60 cells went up as the dose increased, the typical apoptotic cell morphology and the appearance of apoptotic DNA ladder could be observed when treated with 0 - 400 microg/ml TSPG for 48 hours. At the same time and same range of concentration, the expression of bax mRNA increased and the bcl-xl expression decreased gradually. When higher than 400 microg/ml of TSPG was used, cell necrosis appeared and the percentage of apoptotic HL-60 cells even decreased. It is concluded that the apoptosis or necrosis in HL-60 cells can be induced by TSPG at certain range of concentration, and the percentage of apoptosis is dose-dependent. The effect on up-regulation of bax mRNA and down-regulation of bcl-xl mRNA probably play an important role in apoptosis of HL-60 cells induced by TSPG.