This volume reviews our current understanding of the hematopoietic system and toxic effects on its components. The work is arranged in six parts. The first provides a background on hematotoxicology, describes the components of blood and blood-forming organs and reviews the complex process of hematopoiesis. Sections two, three, and four describe toxic effects on erythrocytes, leukocytes and hemostasis, respectively, and include discussions on putative agents and mechanisms, as well as the diagnosis and treatment, of these disorders. Section five addresses human hematopoietic stem cells, which represent an important target tissue that is amenable to in vitro testing. The last section deals with risk assessment in both the clinical and preclinical setting.