Drawing on published and archival materials, this article charts the history of the Society for the Psychological Study of Social Issues (SPSSI)-sponsored Task Force on Sexual Orientation (1978–1982). The Task Force offers a lens through which to explore the assumptions about the nature of human sexuality at work in 1970s psychology. The concept of nature does not possess a stable meaning across disciplinary communities. Where for some nature connotes the normalizing sanction of natural laws, others associate the term with artificial claims about the constraints of a deficient biology. As an organization founded by social psychologists, SPSSI projects, such as its members’ work on race relations, tended to emphasize the latter strategy. Responding to conservatives who cast homosexuality as unnatural, a number of Task Force members turned to sociobiology as a normalizing natural science. In this regard, the Task Force was an important episode in defining what might constitute activist-science.