Here we evaluate Taxol (paclitaxel; Bristol-Myers Squibb, Princeton, NJ) and cyclophosphamide (CY) with recombinant human granulocyte colony-stimulating factor (rhG-CSF) for mobilization of peripheral-blood stem cells (PBSCs) for autologous stem-cell transplantation in patients with breast and ovarian cancer. PBSCs were collected from 17 patients with breast (n = 11), ovarian (n = 5), and gastric (n = 1) cancer after administration of Taxol (170 mg/m2 x 1) and CY (4 g/m2 x 1) followed by rhG-CSF (10 micrograms/kg/d). PBSC collections after Taxol and CY were compared with PBSC collections from nine patients with stage IV breast (n = 8) or stage III ovarian (n = 1) cancer who had received CY (4 g/m2 x 1) followed by rhG-CSF (16 micrograms/kg/d) for mobilization. Mean WBC and platelet counts on the first day of apheresis were 6.3 x 10(9)/L (range, 1.9 to 22.1) and 35 x 10(9)/L (range, 19 to 77), respectively. The median numbers of CD34+ cells, peripheral-blood mononuclear cells (PBMNC), and peripheral-blood total nucleated cells (PBTNC) collected were 13.02 x 10(6)/kg (range, 5.4 to 57.8; mean, 16.02), 6.86 x 10(8)/kg (range, 1.9 to 51.2), and 17.41 x 10(8)/kg (range, 2.4 to 106.6), respectively. In the comparison group, the median yield of CD34+ cells was 6.39 x 10(6)/kg (range, 0.2 to 28; mean, 10.01; P = .01). The mean daily yield of CD34+ cells/kg/collection was 3.5 (range, 0.8 to 28.9) after Taxol and CY, as compared with 1.3 (range, 0.1 to 7.0) for patients who received CY alone (P = .01). All patients who received CY and Taxol reached a target level of 5 x 10(6) CD34+ cells/kg, as compared with five of nine patients (55.5%) who received CY alone (P = .03). These data suggest that Taxol and CY followed by rhG-CSF mobilizes PBSCs in patients with advanced breast and ovarian cancer more effectively than this regimen without Taxol.