Results of bioassays to determine levels of insecticide resistance in recently collected Heliothis virescens (F.) (tobacco budworm) strains to four classes of insecticides are described. Resistance to pyrethroids (determined by the adult vial test) reached levels as high as 77% in Mississippi, 38% in Arkansas, and 58% in Louisiana in 1992. A spray chamber bioassay confirmed resistance to pyrethroid, carbamate, organophosphorus, and cyclodiene insecticides in Mississippi. Topical bioassays using discriminating doses of insecticides confirmed resistance to these four classes of insecticides in Louisiana strains of H. virescens. Tests using piperonyl butoxide showed synergism of cypermethrin, indicating metabolic resistance in strains from Louisiana. Multiple resistance in H. virescens appears to be more wide-spread than previously reported.