Participatory research embodies an approach to data collection that is two-directional--both from the researcher to the subject and from the subject to the researcher. It is a process of collaborative problem-solving through the generation and use of knowledge. It is dynamic, demand-based, and change-oriented, and seeks to raise people ' s awareness and capacity by equipping them with new skills to analyze and solve problems. When carried out in a participatory manner involving users in decision-making, the data collection process itself can foster ownership and involvement in follow-up actions. In addition to identifying the principles underlying participatory research--and how these differ from conventional research methodologies--this document provides guidance on defining the purpose of a study, organizing the participatory research process, choosing from available data collection methods, selecting and training field workers to carry out the research, disseminating and using findings. This document is intended to be used by technical and social science staff involved in planning and implementation of water and sanitation facilities for the poor. With adaptation, the methods have application across sectors. Drawing on experience gained during the past fifteen years in more than twenty countries, the volume also offers a wide array of participatory research activities and checklists.