Cotton genetically engineered to produce the Cry1Ac toxin from Bacillus thuringiensis (Bt) provides an effective management tool for the pink bollworm (PBW), Pectinophora gossypiella (Saunders). Currently, cotton growers are required to plant refuges of non-Bt cotton near Bt cotton fields. Such refuges produce susceptible PBW individuals that mate with rarely occurring resistant individuals, thereby decreasing the frequency of individuals homozygous for resistance. Because the PBW feeds on cotton seeds, pollination of cotton in refuges by pollen from nearby Bt cotton could reduce efficacy of refuges through the production of seeds that express Bt toxin in refuges. In this study, we evaluated the dominance of Bt production in cotton bolls, estimated the extent of gene flow from Bt to non-Bt cotton in Arizona cotton fields, and investigated the effect of distance between Bt and non-Bt cotton on such gene flow. Potential consequences of gene flow from Bt to non-Bt cotton on PBW resistance evolution are discussed.