The myelodysplastic/myeloproliferative neoplasms (MDS/MPNs) lie at the interphase of phenotypically opposing bone marrow malignancies. They are characterized by concomitant features of bone marrow failure and myeloproliferation and are generally associated with a poor prognosis. Although much is unknown with respect to the clinical course and molecular biology of MDS/MPNs, emerging research is beginning to uncover the key defining characteristics of this designation. In this review, we will discuss the features of MDS/MPN diseases that unify there clinical and molecular course and those that define distinct disease entities. We will discuss advances in genetics and MDS/MPN modeling, as well as translational discoveries that are anticipated to inform the diagnosis, prognostication, and treatment of MDS/MPNs in the near future.