The effect of the following four herbicides on weeds, forming secondary weeds in cotton was tested at the Institute of Cotton and Durum Wheat – Chirpan under field conditions during the period 2007-2009: pendimethalin (Stopm 33 EC), oksifluorfen (Goal 2E) oksidiarzhin (Raft SC 400), isoxaflutole (Merlin 750 WG). The herbicides were incorporated in various doses during the budding phase of the culture. It was found that the September yield decreased by 9.2% in Stopm 33 EC, by 10.3% in Raft 400 SC, by 23.6% in Goal 2 F and 49.4% in Merlin 750 WG, when the herbicides were applied in high doses. The vegetative application of those herbicides led to increased early-ripeness of the cotton plants by 3.5% in the version with Merlin 750 WG – 50 g/ha. Reduction of this indicator was reported after spraying Goal 2 E in two tested doses (0.6 l/ha and 0.8 l/ha) by 16.9% to 20.6%.