Cotton (Gossypium hirsutum) is considered an important plant fibers and was cultivated 150-200000 ha in Iran. Damage of pests has been estimated more than 30 percent in Iran. Chemical insecticide like Endosulfan or Metasystox that has adverse effects on the environment are traditionally sprayed 10 to 12 times on cotton during the growing season. In order to reduce the use of pesticide, Bt cotton technology was introduced by developed countries. This method has many advantages, including minimized use of pesticides, better control of insects and pests and more efficient fibers. Although the availability of transgenic seeds is the first controlling factor, but there is urgent need for to produce modern Bt cultivars and also create and improve awareness among farmers about this product. Nowadays there is an increasing trend to use of Bt cotton Due to its significant benefits. The aim of this paper is to evaluate the scientific aspects of risk assessment of transgenic Bt cotton cultivation.