The authors present a cytological study of 200 cases of myelodysplastic syndromes (MDS) [corrected], classified according to the FAB cooperative group. This analysis involves the conventional parameters of the peripheral blood and bone marrow differential counts, the systematic recording of signs of dysmyelopoiesis on the erythroblastic [corrected], granulocytic and megacaryocytic lineages and the assessment of blood granulocytes myeloperoxidase (MPO). On the outside of the typical acquired idiopathic sideroblastic anaemia (severe, isolated anaemia associated with intense dyserythropoiesis), the diagnosis of MDS requires very astute cytological interpretation: indeed, when the dysgranulopoiesis is pronounced, determination of peripheral blood and bone marrow differential count is especially difficult. Conversely when the dysmyelopoiesis is slight, a systematic search of morphology signs [corrected] of its presence must be done and associated with functional studies such as MPO activity technically easy to realize.