Since 1985 measurements of gasses, aerosols, precipitation and throughfall have been carried out at three forest sites in Denmark with equal aged Norway Spruce plantations. The times series show a downward trend in the concentration of sulphur dioxide. Particulate sulphate, ammonia and particulate ammonium and the total nitrate seem to have a more constant concentration level. The wet deposition measurements show a decreasing trend in the content of acid (protons), sulphate, ammonium and nitrate, though for the nitrogen compounds it is only a slight fall. A decrease in concentrations of protons and sulphate is also seen in the throughfall measurements, in throughfall the nitrogen compounds hardly seem to decrease.