Abstract: Abstract:ObjectiveTo study the efficacy and factors that affect peripheral blood stem cell （PBSC）mobilization of patients with breast cancer treated by paclitaxel plus recombinant human G-CSF(rhG-CSF). Methods Twenty-six patients with breast cancer were included in our study.PTX at the dose of 175 mg/m2 was continuously given for 24 hours.When the number of white blood cell reached 1.0×109/L，rhG-CSF was given until the end of leukopheresis.The mononuclear cells （MNC）and CD34+ cells collected by a continuous flow cell separator from peripheral blood were analyzed with FACS.Various factors affecting the yield of CD34+，including age, the lowest leucocyte counts after chemotherapy, the blood cell counts before leukopheresis, pathological stage, prior chemotherapy were analyzed. Results The leukopheresis was started on the median 10th day following mobilization chemotherapy.The mean values of MNC and CD34+cells were (7.89±1.45)×108/kg and (4.88±1.54)×106/kg,respectively.The age was related with CD34+ cells counts.The other factors didn't significantly affect the CD34+ cells counts （P>0.05）.No serious side effect was observed. Conclusion PTX combined with rhG-CSF was an effective and safe mobilization regimen for autologous peripheral blood stem progenitor cells of patients with breast cancer.The age affected the collected number of CD34+ cells.