Since 1990 in Poland, a lot of soils have been changed to fallow. At first, degraded soils from eroded areas were changed. Some of them arc fallow till today. Research work was carried out on the eroded soils that were under intense agricultural use in the 80-ties. Investigations on the superficial layer of these soils were carried out in 1995, after a four-year period of fallow conditions. The investigations concentrated on the changes in chemical properties of the humus horizon (0-20 cm) and changes of biological activity (0-40 cm) formed during the fallow period. The range of changes in the chemical properties was not big. However, biological activity of these soils changed more substantially. A decrease of C organic content was also characteristic. The present authors determined also a decrease of hydrolytic acidity in some soils, according to their location in the relief. In some soils, the content of Mg and K available forms was higher. Some of the soil functions related to habitation were changed too, e.g. visible forms of water erosion stopped.