Evaluation is a set of research methods and associated methodologies with a distinctive purpose. They provide a means to judge actions and activities in terms of values, criteria and standards. At the same time evaluation is also a practice that seeks to enhance effectiveness in the public sphere and policy making. In order to improve as well as judge, there is a need to explain what happens and would have to be done differently for different outcomes to be achieved. It is in this explanatory mode that evaluation overlaps most directly with mainstream social science. This collection offers a complete guide to evaluations research methods. It is organized in four volumes. Volume 1 focuses on foundation issues and includes sections on the rationale for evaluation, central methodological debates, the role of theory and applying values, criteria and standards. Volume 2 examines explaining through evaluation and covers sections on experimentation and causal inference, outcomes and inputs, socio-economic indicators, economics and cost benefit approaches and realist methods. Volume 3 addresses qualitative methods and includes sections on case studies, responsive, developmental and accompanying evaluation, participation and empowerment, constructivism and postmodernism and multi-criteria and classificatory methods. Volume 4 concentrates on evaluation to improve policy with sections on performance management, systematic reviews, institutionalization and utilization and policy learning and design. The collection offers a unique and unparalleled guide to this rapidly expanding research method. It demonstrates how method and theory are applied in policy and strategy and will be an invaluable addition to any social science library. Elliot Stern is the editor of Evaluation: the International Journal of Theory, Research and Practice, and works both as an independent consultant. He was previously Principal Advisor for evaluation studies at the Tavistock Institute, London.