In the Ord River irrigation Area (ORIA) INGARD' cotton varieties have been grown utilising novel integrated pest management systems (Strickland et al 2003). A winter production window, use of specific chemistry and biological control has demonstrated that acceptable yields (7-8 bales/Ha) can be consistently produced with fewer than five pesticide sprays. Aphis gossypii (cotton aphid) has been regarded as a tool in this system. During June/July when HeIiothis and beneficial insect populations are low in cotton, A. gossypii populations increase. This encourages beneficial insects into the cotton from the surrounding area. The beneficial insects feed on the aphids and in August, when Henothis populations increase again there is a resident population of beneficial insects in the cotton. In some years in Kununurra, a pesticide spray for Henothis can be avoided using this method of natural control. Data from eastern Australia suggests that cotton will recover from aphid damage provided infestations do not persist at high levels (>90% plants infested) for too long (<10 days) (Wilson & Spora 2001). These thresholds have riot been validated for winter grown cotton in northern Australia. When cotton is grown in the winter, peak flowering and fruit production occur when day length is short, radiation is low and temperature is low. Growing conditions are far from ideal. Aphids may have a Iarger impact on growth and yield than previously suspected. This paper describes some of the results from a preliminary trial carried out in Kununurra in 2003 examining the impact of aphids on photosynthesis and yield of winter grown cotton.