In order to clarify the relationship between myelodysplastic morphologic features of marrow cells and prognoses and 1.0 define other prognostic factors, 124 patients with the FAB criteria of myelodysplastic syndrome (MIX) were analysed. These included 57 patients with refractory anemia (RA), 5 RA with ring sideroblasts (RARS), 25 RA with excess of blasts (RAEB), 14 chronic myelomonocytic: leukemia (CMML) and 23 with RAEB in transformation (RAEB in T). Univariate analysis of all MDS patients or those of RA demonstrated that the following factors, which were not reported or fully investigated previously, were significantly associated with prognosis. These included neutrophil alkaline phosphatase (NAP) score (significant only for all MDS), the percentage of marrow erythroblasts and lymphocytes present, the percentage of cells with morphological abnormalities in individual cell lineages and the number of cell lineages showing atypia (significant for all MDS and RA). Multiple regression analysis showed that (%) of marrow erythroblasts, NAP score, hemoglobin levels and number of marrow granulocytes with atypia were significant for predicting the prognosis of all MDS patients while the number of marrow megakaryocytes and granulocytes with atypia were significant for prognosis in the subgroup with RA.