Maxwell M. Wintrobe, MD, published the first edition of Clinical Hematology in 1942. Since that time, the book has become a classic in its field. In the preface to the present edition, Dr. Wintrobe acknowledges that with each succeeding edition, it has become more difficult and challenging to encompass all the dimensions of the rapidly expanding field of hematology. For this reason, he has enlisted five very capable coauthors to aid him in the composition of his book. Through their efforts, the book has been reorganized so there are now six major divisions: part 1, "Introduction"; part 2, "The Normal Hematopoietic System"; part 3, "Disorders of the Red Cells"; part 4, "Disorders of Platelets and Hemostasis"; part 5, "Disorders Characterized by Adenopathy, Splenomegaly, and/or Abnormalities of Leukocytes or Immunoglobulins"; and part 6, "Pancytopenias and Myelothesic Conditions." To encompass the additional material, the book is now approximately 600 pages longer than