Resistance in the cotton aphid (Aphis gossypii) is a major new threat to Australian cotton production (Herron et al. 2001). Insecticide monitoring underpins the management of resistant populations and collections of aphids are made from cotton fields, weeds farm gardens and residential backyards. These are tested against a range of the control options allowing us to identify emerging resistance problems as well as keeping track of existing problems. This information then contributes to the development of the aphid component of the Insecticide Resistance Management Strategy (IRMS) for cotton. Management is underpinned by rotation between insecticide groups and restriction in the number of applications of product from any one insecticide group. At present, there are five chemical groups to use in rotation against A. gossypii. In the current insecticide groupings the carbamate aldicarb is in the same resistance management group with pinmicarb and the organophosphates, due to likely cross resistance between these insecticides which fall into the IA and IB Groups. However, there is evidence from testing of resistant aphid strains that cross-resistance within the carbamates and organophosphates cannot be assumed. Hence, aphids that are resistant to pinmicarb or organophosphates may be susceptible to aldicarb or carbosulfan and this would change resistance management options. It was decided to investigate biochemically the potential for cross resistance between these two carbamates and other members of Group IA and IB. It was hoped to be able to separate aidicarb and carbosulfan into their own separate group for resistance management in order to give the growers more flexible control options. Here we report the results of the 2002-2003 and 2003-2004 season&#39s research on aphids and outline the practical implication of those findings for resistance management