Decision analysis has come of age as a methodology and practice for decision making under uncertainty. It has advised policy at the highest levels of business and government and aided individuals in private decisions. Risk analysis, a companion methodology, has been used on countless project and policy evaluations. This special issue comprises descriptions of important applications of decision and risk analysis around the world, a tutorial on state-of-the-art methods, updates of consulting and management practice and methodology, discussion of methods appropriate to government decisions, and provocative opposing essays on the contributions and limitations of decision analysis in practice.