A 26-year old man had pancytopenia and marrow hypoplasia in association with a CD 3+, CD 8+ clonal large granular lymphocyte. At first treatment with cyclophosphamide and prednisone resulted in normalization of the patient's cell counts. During the second episode of illness it was observed infiltration of lymphnodes, stomach and bones. Application of steroids combination chemotherapy was inefective. The patient died.