The aim was the actual aerobic stability of silage, determined in the real conditions in the bunker silo, to compare with the aerobic stabi­lity, measured in the laboratory standard conditions. Silage chop, before the start of fermentation, was sheeting by a plastic-transparent sheet and a black and white tarp that was loaded on the entire surface of the tires. Temperature changes over was significantly different for silage under the tarp, silage after going away of the tarp, and silage stored under laboratory conditions. Differences within and between temperatures were in the silage depths below the surface 5 cm, 20 cm and 35 cm, and between silage maize and lucerne. Pro­portionally with increasing exposure times of oxygen decreased values pH, the acidity of the water extract solution and acid content and conversely was increasing temperature and the content of ammonia nitrogen. In the real conditions in the bunker silo the aerobic stability was affected so much that differed significantly from the stability, established by the standard method in the laboratory.