Recombinant human granulocyte-monocyte colony-stimulating factor (rhGM-CSF) was compared with recombinant granulocyte colony-stimulating factor (rhG-CSF) in 34 patients for mobilization of peripheral blood stem cells (PBSC) and for posttransplantation use. Peripheral blood stem cell mobilization was initiated by a single 1 h infusion of cyclophosphamide (4 g/m2) in all patients, followed by either a continuous infusion of rhGM-CSF (250 micrograms/m2/day) in 17 patients (group A) or a daily subcutaneous injection of rhG-CSF (10 micrograms/kg/day) in 17 patients (group B). PBSC were collected using a Fenwal CS 3000 continuous flow blood cell separator in one to three sessions. All patients suffered from various childhood malignancies. No difference in the number of collected cells among both groups was found. A mean of 2.7 x 10(8)/kg mononuclear cells (MNC) and of 7.9 x 10(4)/kg CFU-GM (colony-forming unit-granulocyte-macrophage) were collected in group A. In group B, 2.3 x 10(8)/kg MNC and 11.8 x 10(4)/kg CFU-GM were collected. In 33 patients, PBSC were reinfused after myeloablative therapy. Patients of group A (n = 17) were treated with rhGM-CSF (250 micrograms/m2/day) starting day +1, and patients in group B (n = 16) were treated with rhG-CSF (10 micrograms/kg/day) i.v. All patients showed a rapid and complete hematopoietic recovery without significant differences in both groups. Time to achieve 0.5 x 10(9)/L granulocytes was 10.9 days in group A and 11 days in group B.(ABSTRACT TRUNCATED AT 250 WORDS)