Field and laboratory studies were conducted to determine the efficacy of six insecticides of different chemistries against the cotton bollworm (Helicoverpa zea) in conventional (‘DPL 5415') and transgenic Bacillus thuringiensis (‘NuCotn 33b') cotton. Treatments included three rates each of Karate^®, Tracer^®, Larvin^®, Pirate^®, Steward^®, and Proclaim^®. The highest rate corresponded to normal grower use rates. Tracer^®, Larvin^® and Steward^® provided good control of bollworms in conventional cotton, with other materials being less effective. However in B.t. cotton, Karate^® was highly effective even at lower rates, as was Tracer^®, Larvin^® and Steward^®. Our data indicated that reduced rates of certain of these insecticides showed considerable promise for bollworm control in B.t. cotton.