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 Verita, Ascona, Switzerland, from June 17 to 19, 1999. It was organized byETH Z]urich, 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...