The aim of this research was to evaluate changes in soil quality associated with the tillage system applied with chosen parameters of soil biological properties. The long-term field experiments were located at a private farm in Rogów (Zamość region, E Poland) on a silt soil and at the Experimental Station in Laskowice (Wroc³aw region, S-W Poland) on a sandy loam soil. Soil samples were collected from 0-15 and 15-30 cm layers. Winter wheat was grown under traditional, reduced and no-tillage systems. The analyses included estimations of microbial biomass C and N content, microbial respiration rate, activity of dehydrogenase and arylsulfatase, and fluorescein diacetate hydrolysis. After eight years the effects of tillage on both soils were clearly noticed. In general, the less disturbing tillage systems enhanced the increase of soil biological activity by 15-40%, on average, than conventional tillage system. The significant correlations between microbial biomass, and/or enzyme activities with total organic C content indicate that concentration of organic C in soil environment plays an extremely important role in enhancing the stabilization and activity of soil microorganisms, and protection of an extracellular enzymes. The studied parameters of soil biological activity showed their sensitivity to tillage applied and may be considered as an useful indicators of soil quality in monitoring all conditions alter soil environment.