Corn treated with herbicide combinations of either atrazine plus pendimethalin or cyanazine plus pendimethalin at different rates give better weed control and higher corn yield. Better weed control is observed during the dry season. Atrazine, cyanazine, diuron and 2,4-D controlled broadleaf weeds but not R. exaltata, C. rotundus and C. monocoides. Pendimethalin alone reduces R. exaltata and controls other grasses, except Boerhaavia erecta and Ipomea triloba. No toxicity of the herbicides used on corn is observed.