Medical and environmental social scientists have recently become interested in how health brings human and nonhuman animals together. is article discusses historical approaches to this question. It then explores applied disease ecology, which examines how anthropogenic landscape change leads to “disease emergence.” The article goes on to review two critical approaches to the question. Critics of bio-security concern themselves with the ways in which animal and human lives are regulated in the context of “emerging diseases” such as avian influenza and foot and mouth disease. Scholarship on human-animal “entanglement” focuses on the ways in which disease, instead of alienating humans from other life forms, brings their intimate relationships into sharper relief. The article argues that health is one terrain for developing a critical environmental analysis of the production of life, where life is the ongoing, dynamic result of human and nonhuman interactions over time.