The results of pH values monitoring performed for 26 years (1988–2013) in Štiavnické vrchy Mts (middle Slovakia) are summarised. The accumulative trend of acidifying components of forest soils downwards the soil depth has been confirmed. The pH values of soil, exposed to a severe airborne pollution load in the past, were in general lower: from 5.42 in the surface humus decreasing to 4.93 at a soil depth of 0.25 m. On the other hand, the pH values of throughfall and precipitation in open area were comparable. The lower pH values were found in lysimetric water within the forest stand plot at 0.10 m depth (4.50 in 2009). The absolute highest pH were found in the forest throughfall and reached the values of 6.40 in year 1999.The annual dynamics exhibited the highest pH values in the winter and spring. On the other hand, the lowest values were recorded in summer period.