The challenge to social theory posed by phenomena of stability in changing social worlds is usually thematized as the dilemma of agency and structure: while human affairs are enacted by agents in unique ways, these agents are not free to enact them as they choose; instead, they must respect the reality of structures. After briefly summarizing the history of solutions to this dilemma, this entry shows how Bourdieu's and Giddens's metatheoretical legitimations of the dialectical dualism of agency and structure gave rise to a 30-year debate about the status and nature of this relationship. Critical realists enriched the debate with philosophical perspectives and attention to the indirect structuring effects of social structures on agency. In contrast, actor-network theory distanced itself from the debate and changed our perspective on the dilemma by ascribing “agency” to things or abstract ideas. Finally, the debate is rephrased to bring out a common denominator of the variety of theoretical and methodological approaches to studying the agency–structure relationship.