Topical diagnostic dose bioassays of representative carbamate, cyclodiene, organophosphate and pyrethroid insecticides were conducted on the LSU laboratory reference colony, a laboratory reference colony from North Carolina and field collected colonies from Louisiana, Oklahoma and Texas. Comparisons between the LSU and North Carolina colonies showed no significant differences in their responses to these insecticides except for significantly higher susceptibility to profenofos exhibited by the North Carolina colony. Significant levels of resistance to cypermethrin, profenofos, methomyl and endosulfan were exhibited by the majority of the field collected colonies compared to the two reference colonies. Bioassays with piperonyl butoxide (PBO) and cypermethrin combinations resulted in significant increases in mortality for five of the twelve colonies tested compared to cypermethrin alone. Significant levels of resistance to thiodicarb were detected in all field collected colonies using a diet bioassay. Data from a field test with cypermethrin and PBO combinations indicated significant reductions in bollworm/tobacco budworm damage and numbers of live larvae were achieved with Ammo® (0.08 lb/acre) + Butacide® (1.0 lb/acre) compared to Ammo® (0.08 lb/acre) alone. These data suggest that metabolic resistance to pyrethroids is widespread in tobacco budworm populations.