Investment projects are an important mechanism for economic development. However, their costs and benefits must be assessed to ensure that the resources committed are being used as productively as possible. This book explains the techniques available to assess the economic impact of projects in developing countries. It draws on the authors' experience in teaching and applying these techniques and combines relevant economic theory with a clear understanding of what can be done in practice. The book aims to make existing techniques readily accessible to both students and practitioners. The second edition has been rewritten with new project examples and the addition of two new chapters on finance and the environment.