This proceedings volume contains a selection of 97 papers presented at the International Conference on Operations Research (OR 2001), the Annual Conference of the German Operations Research Society (GOR). The contributions cover the broad interdisciplinary spectrum of operations research and present advances in theory, development of methods and applications in practice. Subjects covered are transport and traffic, energy and environment, quantitative methods in marketing, production and logistics and supply chain management, finance and banking and insurance, scheduling and project planning, operations research in the health service, continuous optimization, discrete and combinatorial optimization, stochastic optimization and simulation, econometrics and statistics and mathematical economics, decision theory, artificial intelligence and fuzzy logic, information and decision support systems and operations research in the Internet, didactics of OR and public understanding.