The problern of "acid precipitation" has been recognized with growing concern in many industrialized countries. The incorporation of pollutants into cloud and rain elements and their transfer to the ground by "wet deposition" are dominant mechanisms leading to a self cleansing of the tro- posphere but, on the other hand, to hazards to the soil, vegetation and forests. The influence of orographic and meteorological parameters and of the regional distribution of precipitation on the deposition of pollutants are insuffi- ciently known factors. During previous years, several projects and analyses have been initiated to improve our knowledge on the dry and wet deposition of pollutants and on the mechanisms of transport of gaseaus and particulate components from the atmosphere to the ground. Research activities have been supported in different fields and it appeared not only useful but necessary to bring the different research-groups tagether to endorse the communication and cooperation between scientists in the related fields. A symposiumwas arranged in Oberurself Taunus in November 1981 to discuss the results of experimen- tal and theoretical work in the field of deposition and to gain a better understanding of each other's methods, experience and Observations. The proceedings presented in this volume permit a fair sur- vey of the present-day knowledge and will be a useful tool for all working in this field. The meeting would not have been possible without the finan- cial support of the German Environmental Agency {Umwelt- bundesamt) .