The first edition of Williams Hematology (né Hematology) was publishedin 1972. This, our 9th edition, will represent our continued efforts over nearly one-half century to provide the most current concepts of the pathophysiology and treatment of hematologic diseases.

　　The rate of growth in our understanding of diseases of blood cells and coagulation pathways provides a challenge for editors of a comprehensive textbook of hematology. The sequencing of individual genomes, analysis of the “dark DNA” and noncoding RNAs, advances in knowledge in proteomics, metabolomics, and other “-omics” fields, as applied to hematologic disorders, have accelerated the understanding of the pathogenesis of the diseases of our interest. The rate at which basic knowledge in molecular and cellular biology and immunology has been translated into improved diagnostic and therapeutic methods is equally impressive. Specific molecular targets for therapy in several hematologic disorders have become reality, and it is not hyperbole to state that hematology is the poster child for the rational design of therapeutics applicable to other fields of medicine.

　　This edition of Williams Hematology includes changes designed tofacilitate ease of access to information, both within the book and its associated links, and has been modestly reorganized to reflect our greater understanding of the origins of hematologic disorders. Each chapter has been revised or rewritten to provide current information. Four new chapters have been added and other notable changes have been made. Chapter 4 “Consultative Hematology” is new to this edition. The chapter “Epigenetics and Genomics” has been divided into separate chapters to reflect the growth of knowledge in those disciplines. Chapter 14, “Metabolism of Hematologic Neoplastic Cells” is new, as this topic has become the basis of multiple potential drug targets for hematologic disease. A section on “Autophagy” has been added to Chap 15 “Apoptosis Mechanisms: Relevance to the Hematopoietic System,” as the topic is becoming increasingly important for understanding of the physiology of blood cell development; and an independent chapter “Heparin-Induced Thrombocytopenia” (Chap 118) has been created to reflect both its pathophysiologic and clinical importance. Recognizing that at the heart of diagnostic hematology is blood and marrow cell morphology, we have continued our incorporation of informative color images of the relevant disease topics in each chapter, allowing easy access to illustrations of cell morphology important to diagnosis.

　　The 9th edition of Williams Hematology is also available online,as part of the excellent www.accessmedicine.com website. With direct links to a comprehensive drug therapy database and to other important medical texts, including Harrison’s Principles of Internal Medicine and Goodman and Gilman’sof Williams Hematology also includes PubMed links to journal articlescited in the references.

　　In addition, Williams Manual of Hematology will be revised to reflect the diagnostic and therapeutic advances incorporated in the 9th edition of Williams Hematology. The convenient Manual features the most clinically salient content from the parent text, and is useful in time-restricted clinical situations. The Manual will be available for iPhone? and other mobile formats.

　　The readers of the 9th edition of Williams Hematology will note a“changing of (some of) the guard” of our editorial group; Drs. Marcel Levi (a member of the 8th edition of Williams Manual of Hematology editorial group), Oliver Press, Linda Burns, and Michael Caligiuri have joined continuing editors Drs. Kenneth Kaushansky, Marshall Lichtman, and Josef Prchal in the 9th edition.

　　The production of this book required the timely cooperation of 101 contributors for the production of 139 chapters. We are grateful for their work in providing this comprehensive and up-to-date text. Despite the growth of both basic and clinical knowledge and the passion that each of our contributors brings to the topic of their chapter, we have been able to maintain the text in a single volume through scrupulous attention to chapter length.

　　Each editor has had expert administrative assistance in the management of the manuscripts for which they were primarily responsible. We thank Susan Madden in Salt Lake City, Utah; Nancy Press and Deborah Lemon in Seattle, Washington; and Annie Thompson, Rebecca Posey, and Kimberly Morley in Columbus, Ohio for their very helpful participation in the production of the book. Special thanks go to Susan Daley in Rochester, New York, and Marie Brito in Stony Brook, New York, who were responsible for coordinating the management of 139 chapters, including many new figures and tables, and managing other administrative matters, a challenging task that Ms. Daley and Ms. Brito performed with skill and good humor.

　　Kenneth Kaushansky

　　Marshall A. Lichtman Joseph T. Prchal

　　Marcel Levi

　　Oliver W. Press

　　Linda J. Burns