The European Forest Institute (EFI) has five Research and Development priority ar­ eas: forest sustainability, forestry and possible climate change, structural changes in markets for forest products and services, policy analysis, and forest sector informa­ tion services and research methodology. In the area of forest sustainability our most important activity has been the project "Growth trends of European forests", the re­ sults of which are presented in this book. The project was started in August 1993 under the leadership of Prof. Dr. Heinrich Spiecker from the University of Freiburg, Germany, and it is one of the first EFI's research projects after its establishment in 1993. The main purpose of the project was to analyse whether site productivity has changed in European forests during the last decades. While several forest growth studies have been published at local, re­ gional and national levels, this project has aimed at stimulating a joint effort in iden­ tifying and quantifying possible growth trends and their spatial and temporal extent at the European level. Debate on forest decline and possible climate change, as well as considerations re­ lated to the long term supply of wood underline the importance of this project, both from environmental and industrial points of view. Knowledge on possible changes in growth trends is vital for the sustainable management of forest ecosystems.