This updated new edition explores the techniques used to assess the economic impact of projects in developing countries. Blending an academic understanding of economics and development with an accessible style and practical advice, the costs and benefits of investment projects, an important mechanism for economic development, are assessed to ensure that resource allocation is as productive as possible. New material has been added, particularly  on the environmental impact of projects, the role of the discount rate in decision-taking, the application of techniques to estimate willingness to pay for benefit estimation and the quantification of health impacts. Although the basic techniques of project analysis were developed many decades ago, they remain highly relevant to address current concerns, such as population growth, urbanisation, pressure on physical infrastructure, inequality, and the climate crisis. This book aims to provide an accessible overview, drawn from extensive practical experience, of project analysis in developing countries. It will be relevant to students, researchers, and practitioners interested in development economics.