The herbicide fomesafen was found to be selective in preplanting and pre-emergence treatments in cotton (Gossypium hirsutum L.). It was effective due to residual soil activity in controlling some of the most troublesome weeds in cotton fields,i.e., pigweed (Amaranthus spp.), black nightshade (Solarium nigrum L.), velvetleaf (Abutilon theophrasti Medik.) and cocklebur (Xanthium spp.). The best soil activity of fomesafen was achieved from pre-emergence or preplanting applications which were activated when the soil was wetted by rain or sprinkler irrigation, but the herbicide caused damage to the crop’s foliage if rain fell just after the cotton emergence.