To find the relationship between myelodysplastic syndrome (MDS) and refractory monolineage cytopenia, thirteen cases of MDS with early presentation of monolineage refractory cytopenia were analyzed retrospectively. The results were as follows: (1) The percentage of 13 cases with refractory monolineage cytopenia were 5.9% of the total 219 MDS patients in the past 10 years. (2) The median time of patients with monlineage cytopenia to M DS diagnosed was 48.5 +/- 55.3 months. The median times from monolineage cytopenia to MDS diagnosed for patients with neutropenia, erythrocytopenia and thrombocytopenia were 12.5 +/- 9.5 months, 53.8 +/- 54.6 months and 59.2 +/- 65.5 months, respectively. (3) The common characteristics of 13 cases were as follows: (a) the macrocytic erythrocytes in peripheral blood and the percentage of intermediate and late erythroblast in bone marrow were increased; (b) occasionally few cells with dysplasia could be found; (c) all patients with erythrocytopenia and thrombocytopenia transformed to RA and RAS while the most of patients with neutropenia transformed to RAEB subtype; (d) autoantibody could be found in part of the patients. It is concluded that some of refractory monolineage cytopenias in essence are the early states of MDS.