Book excerpt: Operational Expert System Applications in Europe describes the representative case studies of the operational expert systems (ESs) that are used in Europe. This compilation provides examples of operational ES that are realized in 10 different European countries, including countries not usually examined in the standard reviews of the field. This book discusses the decision support system using several artificial intelligence tools; expert systems for fault diagnosis on computerized numerical control (CNC) machines; and expert consultation system for personal portfolio management. The failure probability based troubleshooting expert system for the Airbus A-310; automatic diagnosis of rotating machinery faults; and expert system for naval resource allocation are also covered. This publication is suitable for researchers and specialists interested in the operational expert system applications in Europe.