Analysis of seasonal abundance patterns for the cotton aphid, Aphis gossypii Glover, and its complex of biological-control agents on six cotton cultivars revealed significant differences in aphid density among cultivars during much of the growing season. Cultivar differences were most apparent, with a greater than 3-fold range in aphid densities, during the period of peak aphid abundance. Lower aphid densities were found on cultivars exhibiting the smooth-leaf character. Although significant differences were detected in the levels of some biological control agents among cultivars on some sampling dates, no consistent patterns of activity were observed. Parasitism and predation appeared important early in the season by slowing cotton aphid population growth and possibly instigating its reversal. Entomopathogen infection likely was the primary cause of an aphid population crash observed one week after peak aphid abundance, and continued pathogen activity combined with predation maintained the cotton aphid at low density for the remainder of the season.