The species composition of weed plants in the oilseed rape agrocoenoses in the south part of Western Siberia (Tomsk region) have been studied. There are more than 80 species of weed plants occupied oilseed rape fields on this territory. Euphorbia virgata, Convolvulus arvensis, Stachys palustris, Cirsium setosum and Sonchus arvensis belongs to the most common and widely distributed species of perennial weeds. In the seed lots of Brassica napus L. Metzg. Cultivated in Tomsk Oblast the fruit and seeds of more than 40 weed seeds have been founded.