We investigated the effects of recombinant granulocyte colony-stimulating factor (G-CSF) administration on duration of neutropenia, antibiotic therapy, and hospitalization days in 25 children with malignancies (Group A: 12 leukemia and lymphoma; Group B: 13 tumors) who were undergoing chemotherapy. We compared the effect of G-CSF with a control group of 21 children with equivalent diseases and chemotherapy that did not receive G-CSF treatment. All 25 children received 5 micrograms/kg/day of G-CSF at the end of chemotherapy courses when absolute neutrophil counts were < or = 1000/mm3. The effect of G-CSF on median neutrophil profiles, antibiotic therapy, and hospitalization days was studied for both groups at the 1st and 4th cycle of chemotherapy. During both cycles, children who received G-CSF showed a faster rise of absolute neutrophil count (P < 0.001) and fewer hospitalization days (P < 0.05), and not as many received systemic antibiotic therapy (P < 0.0001). We conclude that G-CSF accelerates neutrophil recovery in chemotherapy-induced neutropenia in childhood malignancies.