The 11th International Symposium on Insect-Plant Relationships (SIP11), held on August 4-10, 2001, in Helsingor, Denmark, followed the tradition of previous SIP meetings and covered topics of different levels from chemistry, physiology, and ethology to ecology, genetics, and evolution of insect-plant relationships. The present volume includes a representative selection of fully refereed papers as well as a complete list of all the contributions which were presented at the meeting. Reviews of selected topics as well as original experimental data are included. The book provides valuable information for students and research workers interested in chemical and biological aspects of interactions between individuals and populations of different organisms.