A series of 27 patients with myelodysplastic syndrome (MDS) was analysed to determine the clinical and pathologic features, the natural history and the prognostic factors. The clinical features of these patients included the following: mean age 53.77 years; symptoms due to cytopenias 100 per cent; hepatomegaly 44.5 per cent; splenomegaly 11 per cent. Almost all patients with MDS presented anemia; additional cytopenias were present in many patients. The bone marrow was hypocellular in 1/3 of cases. The patients have been classified according to the French-American-British (FAB) Group criteria: there were 11 patients with refractory anemia, 11 patients with refractory anemia with sideroblasts and 5 patients with refractory anemia with excess of blasts. The mean survival was 19 months, 9 patients died: death was due to infection or hemorrhage in 7 cases and to evolution to acute myelogenous leukemia (AML) in 2 cases (10.5%). Thrombocytopenia, the Bournemouth scoring system and FAB classification were independent prognostic factors.