Foundations of Risk Analysis presents the foundational issues in risk analysis - expressing risk, understanding what risk means, building risk models, addressing uncertainty, and applying probability models to real problems. The principal aim of the book is to give the reader the knowledge and basic thinking they require to approach risk and uncertainty to support decision making. This new edition presents an updated perspective on risk and risk analysis, reflecting on recent developed theory on the risk concept and its measurement. New material includes an assessment of how risk is defined, understood and described as well as exploring the use of other approaches for representing and characterizing uncertainties than probability; recent developments on risk and uncertainty concepts, representations and treatment are also presented.