Immediate effect of two rates of gel-forming soil conditioner Viterra (0.5 and 1 g kg-1) on soil aggregation, aggregate water stability and water-air properties of Haplic Luvisols developed from loess, subjected to surface water erosion, were studied in a field experiment. The studied soils represented slightly eroded soil, moderately eroded soil and completely eroded soil. The results prove that application of these rates of Viterra significantly decreased the unfavourable clodiness, increased the air-dry aggregate content of 1–5 mm and 0.25–1 mm in diameter in surface layer (0–5 cm) of eroded soils. The soils were characterized by a significantly higher content of water-stable aggregates of 0.25–10 mm in diameter and the favourable mean weight diameter of water-stable aggregates. Hydrogel also exerts a favourable effect on dry bulk density, maximum and field moisture capacity, retention of available water for plants, total porosity and content of macropores. Most effective application was in the rate of 1 g kg-1 of Viterra.