Abstract Given the proliferation of calls to consider sex and gender in biomedicine, it is critical to address how the two concepts, and the relationships between them, are being implemented in a research setting. This chapter considers how we might transcend a simple, binary female–male framing and embrace the idea of the entanglement of sex and gender. The ways that the terms sex and gender are typically used in biology and health research are considered, with a focus on the relationships between these constructs, and areas of coherence and disagreement in their conceptualization. Problems arise when sex and gender are principally operationalized in terms of a female–male binary, including not only the resulting exclusion of trans, nonbinary, and intersex individuals but also the inadequacy of a binary analytical framework to account for context, overlap, in-group heterogeneity, continuity, and similarity. Entanglement and interaction are compared and contrasted, three forms of scientifc engagement with these ideas are identifed, and the implications of intersectionality for the operationalization of sex and gender are considered. In the context of experimentation, an entanglement perspective on sex and gender is explored for what it might enable along with the challenges it presents. As researchers grapple with the incorporation of sex and gender in their work, these frameworks will require ongoing development and refnement, reduced reliance on the dominant binary female–male analytical framing, and a move to a contextual, mechanistic approach that better refects conceptual complexity, diverse