We studied the effects of human urinary macrophage colony-stimulating factor (huM-CSF) on the mobilization of peripheral blood stem cells (PBSC) following cytotoxic chemotherapy in 6 patients with acute leukemia. After complete remission (CR) was achieved, two courses of consolidation chemotherapy consisting of an intermediate dose of cytosine arabinoside were administered to the patients. During a recovery phase after each course of consolidation chemotherapy, two successive cycles of leukapheresis were performed every other day. M-CSF was administered intravenously at a dose of 8 x 10(6) U/day during a recovery phase after the second course of consolidation chemotherapy (cytotoxic plus M-CSF mobilization). There was no significant difference in white blood cell (WBC) or platelet recovery between the first and second cycles, regardless of the administration of M-CSF. Furthermore, between cytotoxic and cytotoxic/M-CSF mobilization, significant differences were not observed in the harvest of mononuclear cells (average 1.43 x 10(8)/kg vs 1.62 x 10(8)/kg), granulocyte/macrophage progenitor cells (CFU-GM) (1.82 x 10(4)/kg vs 3.07 x 10(4)/kg) or erythroid progenitor cells (BFU-E) (2.86 x 10(4)/kg vs 2.66 x 10(4)/kg). Thus M-CSF is not effective for expanding a pool of circulating hematopoietic stem cells when administered at a conventional dose during hematologic recovery following chemotherapy.