Chronic idiopathic neutropenia can occur in spite of the normocellular bone marrowin myeloid series with or without anti-neutrophilic antibody. We report a patient with chronic neutropenia and severe polyclonal hypergammaglobulinemia.The patient demonstrated a positive anti-neutrophil antibody by fluorocytometry, although granulocyte-specific anti-nuclear factor and anti-stem cell (CFU-GM) antibody were negative. Thus, neutropenia of this patient appeared to be due to the antibody-mediated destruction of neutrophils. Both neutropenia and hypergammaglobulinemia were normalized by the administration of prednisone.