AbstractMyelodysplastic/myeloproliferative neoplasms (MDS/MPNs) are rare de novo myeloid neoplasms that exhibit hybrid dysplastic and proliferative features at presentation. This SHP/EAHP Workshop session was uniquely problematic owing to the overlap between MDS/MPNs and both chronic myeloproliferative neoplasms and myelodysplasia. The borderline between MDS/MPNs and overt acute myeloid leukemias was also an issue, mainly related to the accurate and consistent delineation of blast equivalents such as promonocytes. Aside from juvenile myelomonocytic leukemia, genetic features defining specific MDS/MPN subtypes have not been identified. Consequently, there is little change in the 2008 World Health Organization classification of MDS/MPNs compared with the 2001 version.