By serving as experimental models for human disease, animals have been instrumental to constructing biomedical knowledge. On the other hand, animals themselves increasingly benefit from biomedical expertise and technologies, as patients in their own right. Healthy companion animals have recently come to be viewed explicitly as potential sources of human health, which contrasts with the potential for animals to injure people or transmit infectious disease. In studies of biomedical and other health knowledges, nevertheless, only the animal model role has been explored in any depth. In this review article, we sketch and discuss three research concerns that currently inform studies of biomedical knowledge: medicalization and biomedicalization; constructing biomedical knowledge; and a concern with heterogeneity. We conclude that a more comprehensive and nuanced account of contemporary societies will result from further consideration of the importance of animals for how people understand health.