This proceedings volume contains 6 invited state of the art lectures and 50 contributed papers presented at OR 98 held at the Swiss Federal Institute of Technology (ETH) Zurich, 31 August - 3 September 1998. This
4-annual international conference was jointly organized by the Swiss, German and Austrian OR-societies and co-sponsored by SIGOPT. The conference had 450 particpants from 36 countries around the world. The proceedings of this
conference are subdivided according to the eleven sections of the conference, namely - Continuous Mathematical Optimization (8 papers), - Discrete Mathematical Optimization (12 papers), - Stochastic Modelling, Optimization
& Simulation (4 papers), - Econometrics & Statistics (3 papers), - Mathematical Economics, Game Theory & Decision Theory (3 papers), - Banking & Finance (2 papers), - Operations & Production Management (3
papers), - Energy & Ecology (1 paper), - Telecommunication (4 papers), - Logistics & Transportation (10 papers), - Fuzzy Systems & Neural Networks (3 papers), - GOR Diploma Prize (1 paper).