We report the usefulness of granulocyte-colony stimulating factor (G-CSF) for the treatment of severe infection with neutropenia after chemotherapy for acute myeloid leukemia (AML, M3). A 5-year-old boy was admitted because of the first relapse of AML. After 2 courses of chemotherapy, he suffered from right mandibular phlegmon due to Pseudomonas aeruginosa. Since various types of antimicrobial therapy were not effective and neutropenia was still present, we started to give him G-CSF (400 micrograms/m2/day, sc). After 5 days, there was increase in the neutrophil count and remarkable clinical improvements. There was no evidence of AML relapse after the G-CSF the rapy. He was given another course of chemotherapy and then underwent allogeneic bone marrow transplantation from his HLA non-identical, MLC non-reactive sister. This successful case indicates that we should use G-CSF for the management of neutropenic AML patients complicated with severe infection.