Since the first description of Philadelphia chromosome-negative chronic myeloproliferative disorders more than 100 years ago, the diagnosis and therapy of these conditions have been based primarily on clinical experience and judgement. Until recently very little was known about the molecular basis of these diseases. In order to spark research in this area basic scientists and clinicians from various parts of the world have contributed to this volume, the first of its kind to put together the current knowledge. The book deals with the new WHO classification of these disorders, novel aspects of diagnostic pathology, the search for disease-relevant genes utilizing molecular biology and proteomic techniques, the description of the roles of PVR-1 and VHL genes for polycythemias and the discovery of the gene mutation responsible for the idiopathic hypereosinophilic syndrome. A chapter on anagrelide, an important novel drug for the treatment of primary thrombocythemia, is included.