This is the most complete presentation available this far on the acidic deposition issue in Finland representing the main research report of the Finnish Acidification Research Programme (HAPRO), a programme designed to support research in this field between 1985 and 1989 with a total budget of about 50 million FIM (about 11 million USD). Researchers and government agencies all over the Northern hemisphere will find this thorough study invaluable for planning, assessing and comparing research within their own territories. This overview focuses on a wide selection of acidic deposition topics from an analytical perspective, detailing the background, materials, methods and results of different individual studies. Reports include emission inventories, deposition studies, forest vegetation studies, forest soil investigations, lake chemistry surveys, etc. The acidic deposition issue resembles a large-size jig saw puzzle. The pieces presented document early warning observations of acidic deposition damage in Finland and a potential for increasing the damage or decreasing it depending on pollution control measures. Systems of analytical models are also presented which are used to synthesize the different acidic precipitation aspects.