This is the second edition of a very popular book on the use of Bayesian networks for risk assessment and decision analysis. It is aimed at practitioners and students, with a focus on applications and practical model-building using a powerful commercial software tool (AgenaRisk) developed by the authors. The second edition is a substantial update, with five new chapters on learning Bayesian networks, decision making, Bayesian networks in forensics, using Bayesian networks to debunk bad statistics, and football prediction, and updates to the existing chapters throughout the book.