This book provides an overview of the diagnostic classification of the MPN, with relevant examples of the histology; this is still critical in establishing a diagnosis, of course complimenting molecular genetic studies. We next provide an overview of relevant contributors to disease pathogenesis, which will provide a background and rationale for the later chapter on novel MPN therapies (Janus kinase-inhibition and others), especially for myelofibrosis (MF). Because thrombotic and bleeding complications can dominate the clinical course during the first decade of disease in essential thrombocythemia (ET) and polycythemia vera (PV), an entire chapter is devoted toward the epidemiology, pathogenic features, risk factors, and management of this set of complications. An in depth review of epidemiology, clinical features, prognosis, and treatment of ET, PV, and MF is provided in chapters 4–6. Because JAK2 V617F is found in virtually all patients with PV, the impact of this mutation is discussed more extensively in chapter 5. Transplantation remains the only curative procedure for the MPN, particularly MF, but the decision to proceed is challenging for physicians and patients alike, and relevant data on prognosis, conditioning regimens, and outcomes are reviewed. Finally, patients with mast cell diseases and hypereosinophilic disorders present challenges in diagnosis and treatment, and the approach to these issues, as well as an update on management of these BCR-ABL negative MPNs is provided in chapters 9 and 10. This book compliments practical aspects of diagnosis and treatment with insights into disease pathogenesis in a rapidly changing landscape, gearing towards students, residents, fellows, and attendings with a special interest in MPN. We hope the readers will agree, and find this book to be a useful tool for the care of their own MPN patients.