This chapter presents a state of the art summary of myeloproliferative neoplasms (MPN) relation to its biology, epidemiology, disease mechanisms, clinical signs, diagnosis, treatment and prognosis. Myeloid neoplasms and acute leukemias encompass MPN, mastocytosis, myeloid/lymphoid neoplasms with eosinophilia and rearrangements, myelodisplastic/myeloproliferative neoplasms, myelodisplastic syndrome, acute myeloid leukemia, blastic plasmacytoid dendritic cell neoplasms, acute leukemia of ambiguous lineage, B-lymphoblastic leukemia/lymphoma, and T-lymphoblastic leukemia/lymphoma. MPN are a group of diseases characterized by the overproduction of one or more blood cell types by the bone marrow. Chronic myeloid leukemia and other MPN subtypes often present with increased or unexplained bleeding or bruising, frequent or repeated infections, slow healing, pain or discomfort under the ribs on the left side, and excessives weating. Diagnosis of MPN involves laboratory assessment of RBC, WBC, platelet, and other cell levels in the peripheral blood and bone marrow.