The cotton aphid has been the focus of a great deal of research in the years since it was first identified as a serious pest of cotton. Nevertheless, basic questions about the biology and the economic impact of this insect remain. This study was undertaken to evaluate the impact of natural enemies on cotton aphid populations, and to assess the impact of aphids on cotton yield and quality. Four treatments were evaluated (1) an untreated control, (2) a fungicide treatment to reduce the activity of the entomopathogenic fungus Neozygites fresenii, (3) an imidacloprid treatment when aphids were present on 50% of plants, and (4) an imidacloprid treatment when aphids were present on >>50% of plants and natural enemies were present. Studies were conducted for three seasons (1999, 2000, and 2001) in commercial cotton fields with one-acre plots and four replicates of each treatment (total of 16 acres per year). Cotton aphid population development was similar in all three seasons with peak aphid numbers occurring in early July and declining rapidly thereafter as fungal epizootics decimated aphid populations. Imidacloprid applications in early July effectively suppressed aphid populations but were followed closely by fungal epizootics. Arthropod natural enemies were not abundant in the study and had no observable effect on aphid populations. Seed cotton yield and lint quality were not significantly affected by aphid infestations.