Myeloproliferative disorders are a group of clonal haematological neoplasms characterised by proliferation of one or more cells of myeloid lineage. They are the result of acquired mutations in the progenitor cell leading to hyper proliferation or neoplastic expansion of more mature forms of myeloid cells. Cells retain their functional ability with some degree of defects and also lead to suppression of normal stem cells. The most common type of Myeloproliferative Neoplasms (MPN) can broadly be classified into BCR ABL positive (Chronic Myelogenous Leukemia) and BCR ABL negative Disorders (Polycythemia Vera PV, Essential Thrombocytosis ET and Primary Myelofibrosis PMF). There are other rare types which have relatively low incidence like chronic neutrophilic leukemia, chronic eosinophilic leukemia, systemic mastocytosis and myeloproliferative neoplasms unclassifiable. These are the indolent type of haematological malignancies associated with marrow hypercellularity and organomegaly, with gradual progression to myelofibrosis or transformation to acute leukemias. During the dormant course of the BCR ABL negative MPN, they are more prone to thrombo-hemorrhagic complications and the treatment strategy is directed mostly to prevent complications. The past decade; therapies for BCR ABL positive disease (CML) have been a milestone achievement in keeping the disease in remission for many years, preventing major complications and halting the progression of the disease. This book discusses the classification, diagnosis and treatment of myeloproliferative diseases and provides insight on the symptoms and risk factors involved in the diseases.