A 60-year-old woman presented with chronic active hepatitis C whose HCV-RNA genotype was II according to Okamoto's classification and serum HCV-RNA concentration was 104 copies/mL. Agranulocytosis was induced 13 days from the commencement of interferon (IFN)-α 2b (6 MU/day) therapy, so the IFN therapy was immediately discontinued. The agranulocytosis improved rapidly with the administration of a granulocyte colony stimulating factor (G-CSF). The possibility that IFN was associated with maturational arrest of myeloid progenitor cells was considered. During the course of 3 years of follow-up, her liver function has remained normal and serum HCV-RNA remains negative.