this period, an enormous amount of new scientific information has been generated in the area of hematology. This knowledge has been the result of both laboratory-based research and clinical trials. Exciting new data have been reported in virtually all areas of preclinical and clinical hematology research. This new edition serves as a resource for students, residents, fellows, scientists, and practicing physicians who are eager to learn about the science and practice of hematology. This third edition of Hematology: Basic Principles and Practice should be viewed as a work in progress; since the appearance of the first edition of this textbook in 1991, the book has evolved as it relates to content, focus, and size. This evolution reflects, in large part, the new directions and growth of hematology as an academic and clinical discipline. In order to retain the quality and vitality displayed in the first two editions, over thirty new primary authors have been added to this book. This changing of the guard is healthy for a text in order to ensure its timeliness and freshness. A significant number of new chapters appear in this volume. These new chapters represent a commitment by the editorial group to constructive change in order to create an excellent book. The authors have continued to update their chapters several times during the 24 months it has taken to complete this volume. The editors would like to thank the authors for these additional efforts, which assure that the text is up to date and comprehensive.