Doctor Dargeon's short monograph is a remarkable text, with the principal strength derived from its testimony to the author's special devotion to the pediatric patient with these unusual syndromes of the reticuloendothelial system. The book has importance as part of the historical record of the slowly-accumulating published knowledge about the clinical problems of children with histiocytic disease. The illustrative material is of considerable interest throughout, and the introductory section on the anatomy and physiology of the reticuloendothelial system is clear and valuable.