This is a complete revision of a book published in 1948 under the title "Cytologie sanguine, normale et pathologique." The text has been increased from 298 pages with 228 illustrations to 588 pages with 405 illustrations, and the whole treatment of the subject has been improved. In the first edition only occasional references were included; the present edition contains a large number of up-to-date and well-selected references. The author is a distinguished contributor to hematological literature. The purpose of the book is to review the subject of cytology of blood and marrow cells in the light of recent developments in phase microscopy, electromicroscopy, cytochemistry, ultracentrifugation, and the use of polarized, ultraviolet, and fluorescent light. Minute description of the appearance of each cell as prepared with classical staining methods precedes the discussion of observations noted with the new techniques. The material is treated in 15 chapters divided in three main parts.