Designed to provide practical information for the bench toxicologic pathologist working in pharmaceutical drug research, this book presents histopathologic descriptions of lesions noted in drug development. Each section contains information related to the lesion to assist the pathologist in making a determination of the origin of the lesion, the importance of the lesion, and the relevance for assessing human risk. Organ-based chapters include a description of light microscopic and electron microscopic of pathological lesions, differential diagnoses, and biological consequences, pathogenesis and/or mechanism of lesion formation, and expected clinical pathology correlates.