Research was conducted at Maricopa, AZ with EPTC (S-ethyl dipropyl carbamothioate) and butylate (S-ethyl bis(2-methylpropyl)carbamothioate) in 1986 to identify factors that influence the activity of these two herbicides on cotton (Gossypium hirsutum). Butylate and EPTC were applied alone and in combination with other cotton herbicides as either a preplant incorporated or preharrow treatment. The greatest injury to cotton and poorest weed control resulted when butylate or EPTC was applied alone on flat ground and incorporated to a depth of 4 to 6 inches. Adequate weed control and minimal injury to cotton were observed when these two herbicides were applied preharrow or shallowly incorporated (2 inches).