A dissertation submitted to the Graduate School, New Brunswick, Rutgers, The State University of New Jersey in partial fulfillment of requirements for the degree of Doctor of Philosophy Graduate Program in Political Science. This dissertation articulates, and details, the relationship between the anti-apartheid movement and United States policy relations with South Africa between 1960 and 1986. The research is based upon an analysis of an original events data set, interviews with legislators, movement activists, and corporate actors involved in the debate over economic sanctions, and a thorough review of Congressional hearings and movement literature. As demonstrated, anti-apartheid movement influence in the policy process emerged from a dialectical relationship between the capacity of the movement to influence policy and a window of opportunity created from tensions between the executive and legislative branches over control of this foreign policy area. The result of this process was that the movement was able to push adoption of economic sanctions against South Africa further and faster than would otherwise have been the case.