Weed infestation of winter wheat was investigated in the direct sowing, conventional and simplified tillage system conditions during 2000–2002 period. Winter wheat grew after oat and spring wheat, which were cultivated under three different tillage systems. Two-year minimum tillage with an amount of crop residue caused heavier weed infestation than conventional tillage and direct sowing. Additionally, no difference was found in the percentage share of weed species under the conventional and zero-tillage system. Distinct differences in the composition of weed species under particular tillage-systems resulted from the random choice of fields for forecrop during the tested three-year period.