This article reviews twenty years’ experience with the Generalized System of Preferences (GSP) labor rights clause, which was the first significant treaty linking of workers’ rights and trade under U.S. law. Parts II and III recount the legislative process resulting in passage of the GSP and as well as workers’ rights provisions in other bilateral, regional, and multilateral trade arrangements. In Part IV, the authors present case studies of the use of GSP labor provisions in six countries : Chile, Guatemala, Malaysia, Indonesia, Pakistan and Belarus. Part V argues that the willingness of the United States to act unilaterally through the use the GSP has driven a process of bilateral, regional and multilateral action to promote workers’ rights in trade that goes far beyond the GSP program. The authors conclude that, on balance, the GSP workers rights clause has been an important instrument in international labor affairs that has yielded concrete, positive results for workers in many instances.