An 80-year old man was diagnosed as having immune thrombocytopenic purpura based on epistaxis, purpura and by the platelet count 8 x 10(9)/l. Prednisolone and gamma globulin were administered and the platelet count had been kept around 50 x 10(9)/l during his follow up. Two years from the onset of immune thrombocytopenic purpura he was admitted because of leukocytosis (79 x 10(9)/l with 79% monocytes), anemia and thrombocytopenia. Hypercellular bone marrow with dysplasia of three lineages was observed. In the bone marrow cytogenic analysis, a -6, clonal cytogenic abnormality was observed. 45XY, der(6), t(6;6)(q16;q23). He was diagnosed as having chronic myelomonocytic leukemia. This is a difficult case in which it was diagnosed as refractory thrombocytopenia as a subgroup of myelodysplastic syndrome, rather than immune thrombocytopenic purpura. which might have preceded the development of chronic myelomonocytic leukemia.