European beech together with Norway spruce form the skeleton of the Carpathian forestsstability. Their health condition is endangered by a high input of sulphur. The lowest content of sulphates reached in throughfall of beech and spruce ecosystems 5-7 mg.1(-1) and in an open space 6-9 mg.1(-1). Upper content varies between 50-70 mg.1(-1), in spruce ecosystems up to 200 mg.1(-1), in a clear-cut area 35-60 mg.1(-1), in isolated cases even more. In water streams of forested catchments we recorded data within the mast frequent range between 15 to 50 mg.1(-1). A common sign of sulphate dynamics in rainfall is their higher concentration in stands opposite to open areas. A synchronization of sulphate content in throughfall and in rainfall in an open space testifies an expressive exogenous influence of sulphate dynamics. The fact, that the highest quantity of sulphur input penetrates in the forest soil during three spring months (40-75 % of annual deposition) has relevant ecological consequences, which unfavourably influence the health condition of forest ecosystems. Maximum ascertained annual values of input reached 240 kg SO42-, i.e. 80 kg S.ha(-1). At a critical load of soils with an annual maximum amount of 7 kg S.ha(-1), it cannot stay without an influence on the total productivity and stability of ecosystems.