Attempting to encompass adequately the new knowledge that has accrued in the past five years and at the same time produce a readable, single-volume work has been a great challenge to the editors. To accomplish this goal we decided to eliminate the section of the book pertaining to laboratory techniques. This part of the book had been a valuable feature since the First Edition and seemed to fill an important need. More than most medical specialties, hematology is laboratorybased, and having ready access to the required techniques is essential. When we published our first edition it was quite possible for a clinical trainee to take the book to the laboratory and to perform many of the studies that were needed to establish a diagnosis, sometimes, perhaps, with the aid of an experienced special hematology technician. The automation of laboratory procedures has dramatically diminished the role of trainees in performing assays, and while this trend has undoubtedly improved the reliability of the results, it has made it less important for trainees to have detailed information about the specifics of the assays. It does not, however, diminish our belief that trainees should know how the studies are performed and critically interpreted; therefore, we have included discussion of important elements of tests and their interpretation in the text of relevant chapters, In addition, we encourage trainees to consult other standard references or the manuals supplied by the instrument and assay manufacturers or the manuals supplied by the instrument and assay manufacturers for details that we may not have been able to include in this text.