This highly topical volume, with contributions from leading experts in the field, explores a variety of questions about membership based organizations of the poor. Analyzing their success and failure and the internal and external factors that play a part, it uses studies from both developed and developing countries. Put together by a group of prestigious editors, the contributors address a range of questions, including: What structures and activities characterize MBOPs? What is meant by success and what factors account for success? What are the internal (governance structure and leadership) and external (policy environment) factors that account for success? Are these factors replicable across countries or even within countries? What are the constraints to successful MBOPs expanding, or to new ones being formed? What sort of policy environment enables the success of MBOPs, and the formation of successful MBOPs? What types of institutional reforms are needed to ensure the representation of the poor through their own MBOs? This is an insightful work, that will be invaluable for students and researchers studying or working in the areas of international and development economics and development studies.