The germfree animal is reared in the laboratory to be bacteria free; its counterpart, the gnotobiotic animal, is exposed to select microorganisms. Germfree and Gnotobiotic Animal Models brings together the most notable points of early and recent studies and gives reference to the most pertinent literature. Practical applications such as the role of microorganisms in dental caries, cholesterol metabolism, cancer, and Chagas' disease and other parasitic diseases are explored.