We report a case of chronic myelogenous leukemia (CML) with pruritic erythroderma. Hyperhistaminemia, elevated level of plasma interleukin-3 (IL-3), and moderate basophilia were noted in this case. His skin manifestation was resistant to topical corticosteroid therapy and exacerbated in parallel with leukocyte count, plasma histamine and IL-3 levels. To identify localization and production of IL-3 in our case, we performed in situ hybridization on peripheral blood cells and skin biopsy specimen, and detected IL-3 mRNA in myelogenic cells in both specimens.