In November 1988 the "'Third Oberursel Symposium" devoted to the problems of input of pollutions into forest-ecosystems and their effects on plants or soil convened. After several years of intensive research on the effects of pollutions on forest­ ecosystems it is obvious that not a single specific pollutant can be made responsible but a mixture of several components act together or interact with each other. The contributions of the workshop _ reflect to a large extend the results of research­ projects which were started at the beginning of the eighties. They review our improved knowledge on the patterns of concentration, of the mechanism of wet and dry deposition and fog interception, modelling studies and the effect of the processes on plant­ receptors and surfaces. Since the 1985 symposium the pathways of pollutants leading to biological damage have been examined and are more clearly recognised. The book reflects the common interest and the continuous effort of scientists from many different disciplines to better understand the physical and chemical processes which finally lead to the observed damage of forest-trees. Comparing the conclusions of the contributions of this book _ with the results of the first Oberursel symposium in 1981, our knowledge on the relevance of the different mechanisms leading to forest-decay has been considerably improved. The book indicates also in which directions future work should be concentrated. Again, I have to thank the authors for their cooperation by submitting their recent research-results.