A female patient developed cutaneous genuine histiocytic lymphoma at the age of 57. The chief clinical manifestation was monomorphous cutaneous nodules. In the early stage her general condition was good. Physical and laboratory examinations showed no abnormality. Histopathologically uniform tumor cells diffusely infiltrated between the collagen bundles throughout the whole dermis of the cutaneous nodules. The cells were proved to be atypical histiocytes by enzyme cytochemical, immunologic and electron microscopic examinations and further confirmed by long term tissue culture. Clinical outpatient treatment had no effect but CCNU produced temporary marked effects. Due to leukopenia the therapy was discontinued; the skin lesions recurred and the patient died of cachexia. The whole course was one year and eight months.