Soil erosion is a problem in many regions of the world, especially in mountainous areas. The main aim of the study was to determine the regularity and factors affecting soil erosion on a Carpathian slope based on long-term (1969–2000) measurements, taking into account meteorological conditions and different forms of land use and land cover (LULC). The highest average annual soil erosion was noted for potato plots (25.7 Mg ha-1year-1); this value was 340 and 19 times higher than on grassland and cereal plots, respectively. For the first time in the Carpathians, the threshold of an extreme erosion event on agricultural slopes was determined in reference to a single event (20 Mg ha-1) or to annual values (48 Mg ha-1). The cover-management factor (C-factor) of the Western Polish Carpathians’ scale was also estimated based on the longest study of soil erosion conducted at the Research Station in Szymbark (Institute of Geography and Spatial Organization, Polish Academy of Sciences). In the analysed catchment, the soil erosion estimate based on the Revised Universal Soil Loss Equation (RUSLE) using the C-factor calculated from measurements was 69% lower than mean soil erosion with the C-factor estimated for Poland. This indicates that the C-factor is the most important factor in policy and land-use decisions. The results are representative of mountain agricultural slopes and are also a key to agricultural production and sustainable development.