Using a lifecycle perspective, the paper I introduce in this seminar analyzes the use of reserved seats and the evolution of cooptation norms and practices in Burundi between the signature of the Arusha Peace and Reconciliation Agreement in 2000 and the 2020 legislative elections. Why have reserved seats and cooptation been introduced in Burundi? What has been their application at the time of the 2005, 2010, 2015 and 2020 elections? What effects did they produce? Value-driven objectives, such as minority protection, only partly explain their use and design. The adoption, functionality and recent transformation of electoral cooptation were also determined by realpolitik, most notably by the elites’ struggle for positions and the balance of power. Cooptation had important effects on ethnic cohabitation within parliamentary factions. The paper contributes to the literature on the micro-institutions of political representation and power-sharing.