This article examines claims made by behavioral endocrinology and biological psychology about the role of sex hormones in producing sex differences in human and animal behaviors. While critiques of biological determinism are common in feminist thought, the author argues that more attention needs to be paid to how scientists attempt to account for social factors and the interrelationship between biology and the social. Dismissing the role of biology entirely remains an inadequate approach for feminism. The author aims to navigate a middle way in approaching the biological and its relationship to the social in understanding sex differences in behavior.