Field experiments were conducted in Michigan, Minnesota, and Wisconsin to evaluate injurious interactions between nicosulfuron herbicide applied POST and nine insecticides applied at planting on ‘Pioneer 3751’ field corn in 1991. Insecticides were applied in-furrow, T-band, and surface band at planting. Corn injury from nicosulfuron and terbufos applications was more severe in Wisconsin than in Michigan. No corn injury was observed in Minnesota. Terbufos 15% ai granule (15G) or 20% ai controlled release granule (20CR) increased nicosulfuron injury to corn in Wisconsin. Nicosulfuron at 35 g ai/ha caused the greatest vigor reduction following terbufos 15G, intermediate vigor reduction following terbufos 20CR, phorate 20G, or phorate 20CR, and the least vigor reduction following fonofos, chlorpyrifos, chlorethoxyfos, tefluthrin, or carbofuran in Wisconsin.