In the Macon Ridge region of Louisiana, there were numerous reports of less than satisfactory insecticidal control of tobacco budworm (TBW)/bollworm (BW) in cotton during 1990. These reports were not confined to pyrethroids, but also included organophosphate (profenofos and sulprofos) and carbamate (thiodicarb) insecticides. One factor responsible for poor control was the abnormally high infestations of these pests during July and August. Results of topical application laboratory tests on L3 stage larvae from a field culture of TBW collected near Hebert, La., found increases in LD(50) values of 18x, 7x and 7x for cypermethrin, profenofos and sulprofos, respectively, compared to values for the LSU-lab strain. Using the spray table bioassay, there were significant reductions in the susceptibility of L3 stage larvae of this field collection to these same insecticides and also to acephate, cyfluthrin, methomyl, and thiodicarb. In other areas of Louisiana, changes in insecticide susceptibility of TBW to pyrethroids, organophosphates and carbamates were found, but in most cases, low population pressure prevented control failures from occurring. Annual monitoring of TBW susceptibility to pyrethroids with adult vial tests indicates substantial increases in pyrethroid resistance in populations in the Macon Ridge region.