This book constitutes the thoroughly refereed post-workshop proceedings of the 27th International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2001, held in Boltenhagen, Germany, in June 2001.The 27 revised full papers presented together with two invited contributions were carefully reviewed and selected from numerous submissions. The papers provide a wealth of new results for various classes of graphs, graph computations, graph algorithms and graph-theoretical applications in various fields.