The myelodysplastic syndromes are a group of heterogeneous acquired and clonal disorders that are characterized by the intramedullar, abnormal death of myeloid progenitors leading to peripheral variable cytopenias. Progressive, aregenerative anemia irresponsive to B12, folates or iron supplementation often constitutes the initial complaint. The diagnosis that may be difficut relies to a careful analysis of bone marrow aspirate morphology Classification system is based on cytogenetic abnormalities, and both the number of lineage involved, and bone marrow blasts. It is predictive for the risk of transformation in secondary acute myeloid leukemia.