The purpose of this study was to determine the effects of Arbuscular Mycorrhizal (AM) fungi mixture-Tetranychus urticae and Glomus intraradices-T. urticae associations on gossypol concentration levels of Carmen and Stoneville cotton cultivars. The effects of treatments on gossypol synthesis were determined separately in four different plant growth periods (15, 30, 45 and 60 days after cotyledons occurring) of the two cotton mean gossypol concentration values of AM fungi and T. urticae association trials were higher than Carmen in Stoneville cultivar in 15-day old plants. Association with G. intraradices-T. urticae and AM fungi mixture-T. urticae produced significant effects in the 30-day old plants in both cotton cultivars (P <0.05). In 45-day old plants, no differences were found in the mean gossypol concentration values of AM fungi and T. urticae association in G. intraradices treatment for both cotton cultivars. Whereas mean gossypol concentrations of the G. intraradices trials were not different from each other in Carmen cultivar in 60-day old plants, mean value determined in AM fungi mixture (0.709 +/- 0.080 mu g/mL) in Stoneville cultivar was different from the other trials (P <0.05).