This article has two goals, an intellectual history of gender as a concept and to outline a framework for moving forward theory and research on gender conceptualized as a structure of social stratification. The authors’ first goal is to trace the conceptual development of the study of sex and gender throughout the 20th century to now. They do this from a feminist sociological standpoint, framing the question with particular concern for power and inequality. The authors use a modernist perspective, showing how theory and research built in a cumulative fashion, with empirical studies sometimes supporting and sometimes challenging current theories, often leads to new ones. The authors then offer their theoretical contribution, framing gender as a social structure as a means to integrate the wide variety of empirical research findings on causal explanations for and consequences of gender. This framework includes attention to: the differences and similarities between women and men as individuals, the stability of and changing expectations we hold for each sex during social interaction, and the mechanisms by which gender is embedded into the logic of social institutions and organizations. At each level of analysis, there is a focus on the organization of social life and the cultural logics that accompany such patterns.