This volume contains a selection of papers referring to lectures presented at the symposium "Operations Research 2004" (OR 2004) held at Tilburg University, September 1-3, 2004. This international conference took place under the auspices of the German Operations Research Society (GOR) and the Dutch Operations Research Society (NGB). The symposium had about 500 participants from more than 30 countries all over the world. It attracted academicians and practitioners working in various fields of Operations Research and provided them with the most recent ad­ vances in Operations Research and related areas in Economics, Mathematics, and Computer Science. The program consisted of 4 plenary and 19 semi-plenary talks and more than 300 contributed presentations, selected by the program committee, to be presented in 20 sections. Due to a limited number of pages available for the proceedings volume, the length of each article as well as the total number of accepted contributions had to be restricted. Submitted manuscripts have therefore been reviewed and 59 of them have been selected for publication. We would like to thank the GOR-board for the abundant collaboration, which we always found to be helpful and fruitful. We are grateful to all the review­ ers, which were asked to review one or more submitted papers. Finally, we would like to thank our colleague Annemiek Dankers and Barbara Fess from Springer-Verlag for their support in publishing this proceedings volume.