Book excerpt: Aiming to support the development of a framework for the analysis of risk in project design and economic analysis, this handbook outlines technical approaches to modeling risk. Also summarized is the nature and practice of sensitivity analysis in dealing with uncertain outcomes as well as the principles to consider in typical risk analysis situations sector by sector. Case studies are included to demonstrate the application of quantitative risk analysis using actual Asian Development Bank projects to help improve project design and quality. Handbook users will learn to identify factors that are the key determinants of project outcomes, determine the likelihood of an individual project's returns being unacceptable, and design measures to mitigate the risks arising from the identified key factors.