These proceedings fonn the outcome of an International Conference on "Impacts of Global change on Tree Physiology and Forest Ecosystems ", held from 26-29 November 1996, at Wageningen, The Netherlands. The conference brought together biologists, ecologists, and forest scientist working in the field of impacts of elevated CO and air pollution on tree physiology and forest ecosystems, and marked the 2 completion of a European COST action on "Impacts of Elevated C02 levels and Air Pollutants on Tree Physiology" (ICAT / COST-614), as well as the conclusion of the frrst phase of an EU-funded project entitled "Long-Term Effects of C02 and Climate Change on European Forests (LTEEF) ", that was carried out under the Environment and Climate Programme of the 4th Framework Programme (contract no's EV5V-CT94-0468 and PECOINIS-CT94-0112). The conference aimed to present an overview of current knowledge of effects of air pollution and climate change, at the biophysical, biochemical and physiological level of trees, against the background of climatic conditions and natural stresses. For the proceedings, we have asked the authors to provide an overview of their recent work, providing an entrance to a particular field of research rather than presenting unpublished material. The meeting took place at the International Agricultural Centre (lAC) with fmancial support provided by the COST-614 secretariat in Brussels. We like to thank mrs. A. van der Bunte of lAC for her support in organising the meeting, mr. A. J. H.