The 25th International Workshop on Graph-Theoretic Concepts in Computer Science (WG'99) celebrated the anniversaryof the workshop series at the Centro Stefano Franscini on Monte Verit'a, Ascona, Switzerland, from June 17 to 19, 1999. It was organized byETH Zurich, sponsored byETH, the Centro Stefano Franscini, the Swiss National Science Foundation, and Swissphone. The workshop looks back on a remarkable tradition of a quarter century, with predecessors organized at various places in Europe. WG'99 has been an insp- ing mix of questions from theoryand practice, and of 74 young scientists and established researchers from all over the world, including Bangladesh, Belgium, Canada, the Czech Republic, France, Germany, Israel, Italy, Japan, Korea, the Netherlands, Russia, the Slovak Republic, Spain, Sweden, Switzerland, the UK, and the USA. Four invited lectures re?ect the history, theory, practice and this year's s- ting. Hartmut Noltemeier as the onlyone of four founding members of the WG series who served on the program committee throughout the entire historyof WG talked about past achievements and future challenges of WG and of the ?eld. Susanne Albers lectured on the theoryof online algorithms. Thomas Lengauer presented practical packing problems from the textile and car manufacturing industries, as well as their solutions. A workshop held at the Centro Stefano Franscini traditionallyo?ers a talk that is open to the general (Italian speaking) public - Nicola Santoro delivered this Stefano Franscini talk byreporting on computer science, school, and community, as seen from the eye of the storm.