This case study is part of six country case study reports that were commissioned in 2003 by the World Bank specifically for the purposes of a summary report on the design and implementation of household targeting systems in the following countries: Chile, Colombia, Costa Rica, Mexico, Brazil and the United States. The report was prepared at the request of officials from the Ministry of Social Assistance. It seeks to examine Brazil's main existing beneficiary registry and selection mechanism. While targeting can effectively channel resources to the poor, implementation details matter tremendously to distributive outcomes. Several key factors affect performance, including: data collection processes; information management; household assessment mechanisms; institutional arrangements; and monitoring and oversight mechanisms. This report conducts an in-depth assessment of key design and implementation factors and their potential impact on outcomes for the household targeting system Cadastro Unico used in Brazil to target social programs to the poor and vulnerable.