There is speculation that current secondary pests of cotton may be more troublesome following the introduction of transgenic cotton. There is concern that increased sprays targeted at the secondary pests, such as cotton aphid, may exacerbate resistance. To quantity resistance in cotton aphid eleven strains were collected from Qld, NSW, NT and WA and tested. Carbamate and organophosphate resistance was detected in strains from Qld, NT and WA but not NSW. Profenofos resistance was low (max. 4.7x), omethoate resistance high (max. 42.1x) and pinnxicarb resistance extreme (max. 1,736x). Low level endosulfan (max. 1.4x), and pyrethroid resistance (max. 4.1x esfenvalerate) was detected in one NSW strain. The implications of the findings of this continuing study are discussed.