Does gender equality in public meetings improve as women’s numbers grow? Research applying critical mass theory to the exercise of influence in public discussion and decision making reveals a complicated story. Women have made significant progress in education, employment, and the attainment of elected office; yet, they continue to lag behind their male counterparts in substantive, symbolic, and authoritative representation. Across political, nonpolitical, and experimental settings, women’s participation and influence does not follow necessarily from their numerical proportion. We review previous studies of how women’s lower status is manifested in group interaction, and we argue that research can better identify when and how numbers matter by attending to the group’s context, institutional features, and informal norms. We describe cutting-edge research designed to explore the effects of institutional rules and norms on women’s authority. Women’s increasing numbers in positions of potential influence constitutes a timely, promising, and challenging agenda for further scholarship.