The research examines the forces that affect the deliberation and passage of gender-related policy in the Brazilian Chamber of Deputies. It analyses the formal and informal institutions that organise the legislative environment and influence gender policy processes and outcomes. I developed an original database that traces all 1,561 gender-related bills deliberated in the lower house for the past 20 years, through each stage of the legislative process. I make a comparison between three different governments and present a detailed examination of bill content through both quantitative and qualitative analyses and interviews with members of the women’s caucus. The thesis is divided into three parts. First, the historical background, description of the case study and mapping of the formal and informal networks, connections and rules that affect gender policy. Second, the collection and analysis of evidence in each government using five variables: legislative agenda control; the executive; the women’s caucus and women’s movements; international agreements; and religiously-based opposition. And third, a comparison between the three governments and the trends seen in terms of the different themes deliberated. The research shows that there was a clear increase in gender bills presented and enacted over time as a result of changes in the institutional context, in particular the election of the Workers’ Party (PT) and the establishment of a Women’s Policy Agency. Although action by women’s organisations during all stages of the legislative process was a fundamental condition for positive outcomes, on its own it would not have been sufficient to accomplish change. The ability of the women’s caucus and women’s movements to reach their goals varied depending on the institutional context. Influential forces such as party elites and the elected executive played a key role.