This proceedings volume contains a selection of papers presented at the International Conference on Operations Research (OR 2003). The contributions cover the broad interdisciplinary spectrum of Operations Research and present recent advances in theory, development of methods, and applications in practice. Subjects covered are Revenue Management, Telecommunication, Information Technology, Production, Logistics, Supply Chain Management, Services, Transportation, Traffic, Scheduling, Project Management, Marketing, Data Analysis, Energy, Environment, Health, Finance, Banking, Insurances, Simulation, Continuous Optimization, Discrete and Combinatorial Optimization, Applied Probability, Artificial Intelligence, Fuzzy Logic, Neural Networks, Econometrics, Statistics, Mathematical Economics, Decision Theory, Experimental Economics, Game Theory, Auctioning, Web Technology, Knowledge Management, Decision Support Systems.