This volume brings together a range of contributors from Europe and North America. All contributions were especially commissioned with a view to e- cidating a major multidisciplinary topic that is of concern to both academics and practitioners. The focus of the book is on expert judgment and its interaction with decision support systems. In the first part, the nature of expertise is discussed and characteristics of expert judges are described. Issues concemed with the eval- tion of judgment in the psychological laboratory are assessed and contrasted with studies of expert judgment in ecologically valid contexts. In addition, issues concerned with eliciting and validating expert knowledge are discussed. Dem- strations of good judgmental performance are linked to situational factors such as feedback cycles, and measurement of coherence and reliability in expert ju- ment is introduced as a baseline determinant of good judgmental performance. Issues concerned with the representation of elicited expert knowledge in kno- edge-based systems are evaluated and methods are described that have been shown to produce improvements in judgmental performance. Behavioral and mathematical ways of combining judgments from multiple experts are compared and contrasted. Finally, the issues developed in the preceding contributions are focused on current controversies in decision support. Expert judgment is utilized as a major input into decision analysis, forecasting with statistical models, and expert systems.