Present classification schemes of bladder neoplasms are based on structural analyses of histologic material, primarily at the light microscopic level. Attempts to identify histologic variables of certain bladder lesions as biologic precursors of malignancy are in progress. Efforts to relate functional attributes of altered bladder tissues to preneoplastic and neoplastic structural changes are in active development. These advances do require a common recognition and communication of histologic patterns that are used as standard benchmarks. This volume is offered to present in detail description of histologic characteristics of bladder cancer in humans and animals. Areas of recent research advances that may extend our knowledge of the pathobiology of bladder cancer are emphasized. Observations derived from experimental animals are related to the pathogenesis of bladder cancer in humans. This book is intended for pathologists, urologists, oncologists, radiation therapists, epidemiologists, environmental scientists, toxicologists, public health scientists, and regulatory officials.