A complex of pests attacks the Australian cotton crop, none more important than the cotton bollworm, Heliothis armigera. and insecticides are considered necessary for its control. H. armigera has a long history of insecticide resistance in Australia. To DDT in the early 1970's and more recently, in 1983. to the synthetic pyrethroids. Since 1983 , H. armigera insecticide resistance has been the subject of an insecticide resistance management program in NSW and Queensland. A knowledge of resistance mechanisms is fundamental to the resistance management strategy, so management can be targeted at avoiding or counteracting the mechanisms.