This publication presents an overview of contemporary interests in tree physiology research within the European tree physiology EUROSILVA network, which has been in operation since 1986. The last phase, entitled COST Action E6: EUROSILVA Forest Tree Physiology Research, was accomplished during the period from 1996 to 2000. The scientific discussions in the three working groups (I: Tree growth and development, II: Tree nutrition and water relations, III: Biotic and abiotic interactions in trees) have touched on a diverse collection of topics. The articles in this book have been written by well-known European and American scientists and focus on basic tree physiology and trees and their environments. The book should provide to the reader information of the EUROSILVA network’s activities and recent findings. Some important future aspects are also discussed.