Myelodysplastic syndromes (MDS) are a heterogeneous group of acquired bone marrow disorders characterized by ineffective hematopoiesis with cytopenia and dysplasia and an increased risk of transformation into acute myeloid leukemia. In patients with MDS the International Prognostic Scoring System (IPSS) is used for characterization and prognostic evaluation under consideration of the blast count in bone marrow, the number of cytopenias and cytogenetic risk group. In a large multicenter study (Greenberg et al: Blood 2012; doi:. 10.1182/blood-2012-03-420489) it has now been shown that the cytogenetic findings at diagnosis allow a more detailed prognostic evaluation of patients with MDS and that in the future should be given a higher priority in the IPSS. The assignment of chromosome aberrations to five (instead of the previously three) risk categories and the re-evaluation of two double and complex aberrations permits a better classification and prognostic assessment. In addition to the established prognostic groups (poor, intermediate and good), two additional categories (“very poor” or “very good”) were introduced and better demonstrate the biological heterogeneity of the disease.