A 31-year-old woman admitted because of fever, chilling and sore throat for 4 days. The symptom was developed after receiving methimazole 20mg per day and carteolol 10mg per day due to Graves disease during last 4 weeks. Physical examination revealed hyperemic enlarged tonsils with whitish plaque. The peripheral blood total neutrophil count was 1,400/mm3 (absolute neutrophil count, ANC 36) and a peripheral blood smear revealed rare neutrophil with lymphocytosis. On the first day of hospitalization, the patient was severely ill with ANC 0, it was decided to administer G-CSF 2ug/kg daily. On the fifth day of hospitalization, ANC in peripheral blood count was persistently zero and bone marrow aspiration and biopsy were performed, which revealed hypocellularity and myeloid hypoplasia. G-CSF given daily for 7days, it was discontinued when the ANC reached 1,539/mm3. The availability of G-CSF may help to shorten the course of agranulocytosis and to reduce its mortality rate.