The aim of this study was to evaluate the weed infestation of 14 winter wheat varieties, grown in organic farming system in 2011, in three locations: Osiny (Lublin voivodeship), Chwałowice (Masovian voivodeship) and Chomentowo (Podlasie voivodeship). The analysis included assessment of the number of weeds and their dry matter in tillering and dough stage. In tillering stage the smallest number and dry matter of weeds were found in wheat varieties cultivated in Osiny. Despite the large abundance of weeds in Chomentowo and Chwałowice (over 100 plants? m-2), there were mainly minor seedlings whose weight did not exceed 20 g? m-2. In dough stage of winter wheat the smallest dry matter of weeds was observed in varieties cultivated in Chomentowo (39 g? m-2 on average), and the largest in Chwałowice (73 g? m-2 on average). Among the tested varieties Nateja and Jantarka were characterized by a big competitive ability against weeds in all locations. In Chwałowice and Chomentowo Ostroga was distinguished by a small number and dry matter of weeds throughout the growing season, as well as Kohelia, Bogatka and spelt Schwabenkorn in Osiny. The large biomass of weeds was recorded in Ostka Strzelecka and Natula in Osiny and Chomentowo as well as Natula, Alcazar and Batuta in Chwałowice.