The need for social safety nets has become a key component of poverty reduction strategies. Over the past three decades several developing countries have launched a variety of programs, including cash transfers, subsidies in-kind, public works, and income-generation programs. However, there is little guidance on appropriate program design, and few studies have synthesized the lessons from widely differing country experiences. This report fills that gap. It reviews the conceptual issues in the choice of programs, synthesizes cross-country experience, and analyzes how country- and region-specific constraints can explain why different approaches are successful in different countries.