No clear consensus has emerged in the debate about the risks posed by transgenic crops and how to assess these risks accurately. In the meantime, interest is growing in strategies to impede transgene movement. This attention is being driven, in part, by expanding interest in using transgenic crops to produce pharmaceutical and industrial products. Potential strategies to impede transgene movement have been published in the scientific literature, and numerous patents have been submitted; however, the efficacy of such strategies has still to be evaluated in a field situation. In this review, we discuss some of the genetic strategies that could be used to restrict the spread of transgenes, although at present many of these technologies are still largely at a theoretical stage of development.