Hematopoietic growth factors ( HGFs) are now known to influence the function of mature myeloid cells as well as their traditional roles as regulators of hematopoiesis. It became apparent that they could take part in inflammatory and immune responses by activating monocytes/ macrophages to release mediators of such responses. We describe a 53-year-old male who developed acute inflammatory arthritis by granulocyte-macrophage colony-stimulating factor ( GM-CSF) following autologous stem cell transplantation for cryoglobulinemia. Arthritis improved dramatically soon after GM-CSF was withdrawn and steroid therapy was admitted. This case may lead to further attention for this potential problem since HGFs are frequently used in a variety of clinical settings.