Field studies were conducted between 1997 and 1999 to evaluate weed control efficacy and the tolerance of BXN cotton to bromoxynil applied over the top of cotyledon to 2 to 4 leaf cotton and post directed at layby. Bromoxynil provided 95 to 100 percent control of most annual broadleaf weeds tested including: Chinese thornapple (Datura ferox), black and hairy nightshade (Solanum spp.), common lambsquarters (Chenopodium album L.) and velvetleaf (Abutilon theophrasti). Best control was achieved with one application of bromoxynil at 1.0 lb. ai/A, but most weeds were also completely controlled with the 0.50 lb. ai/A rate. Control of pigweed (Amaranthus spp.) was erratic and poor to moderate at all rates tested. Control ranged from 15 to 80 percent, but when bromoxynil was tank mixed with any of the selective grass herbicides (clethodim, fluazifop-p or sethoxydim) control was reduced to completely unacceptable at 4 to 5 percent. There was no advantage in control of the above weed species when bromoxynil was applied in a tank mix with pyrithiobac sodium or MSMA. Control of annual morningglory (Ipomea spp.) has been slightly more difficult. Bromoxynil applied over the top to annual morningglory provided acceptable control for 35 days when followed by a post directed treatment. Either a single over the top or single later post directed treatment provided unacceptable control. At 90 days after treatment control was also unacceptable with an over the top followed by a post directed treatment. Best control was achieved when bromoxynil was applied to morningglory with 2 or fewer leaves and control was enhanced when tank mixed with MSMA.