This proceedings volume contains a selection of 87 papers presented at the Symposium on Operations Research (SOR 99) that was held at the Otto-von-Guericke-University of Magdeburg from September 1-3, 1999. The contributions cover developments in Mathematical Programming, Combinatorial Optimization, Graphs and Complexity, Control Theory, Stochastic Models and Optimization, Econometrics and Statistics, Mathematical Economics and Economic Theory, Game and Decision Theory, Experimental Economics, Artificial Intelligence, Neural Networks, and Fuzzy Systems, Information and Decision Support Systems, Finance, Banking, and Insurance, Scheduling and Project Planning, Transport and Traffic, Inventory and Logistics, Production, Marketing, Energy, Environment, and Health. In this broad field of subjects where Operations Research is applied both, most recent advances in theory and new successful applications to practice, are reported.