The effect of different levels of compression (A₁ = 420 gdm^-1, A₂ = 560 gdm^-1) and inoculation (B₁ = no inoculant, B₂ = with inoculant) on changes in chemical composition, proteolysis and quality of lucerne silage was investigated in this paper. Based on the results of chemical analysis we found that in silages with more compressed material there was a reduction in the amount of ammonia nitrogen, soluble nitrogen and acetic acid, and increased content of protein nitrogen (‘true’protein) and production of lactic acid (p<0.05). With the inoculation of the ensiling material the production of ammonia nitrogen and acetic acid was reduced but the content of lactic acid and acidity was increased (p<0.05). The interaction of both investigated factors (AXB) induced a decrease in the proteolysis degree, increase of lactic acid production and decrease in acetic acid production, and decrease in pH values (p<0.001) in investigated silages. The investigated factors had less influence on the chemical composition of lucerne material, and the significant variations were observed in fat and NFE contents. On the basis of this investigation the degree of compression is the most important parameter in ensiling technology. With the adequate compression and reduction of air in the starting material, the aerobic phase is reduced and the activity of proeolytic enzymes is decreased. In practice the special attention should be given to factors on which directly or indirectly the level of compression of ensiled material depends: wilting, cutting, object selection and/or selection of machines used for compression.