American agricultural employers have long utilized foreign workers on a temporary basis, regarding them as an important labor resource. At the same time, the relatively low wages and adverse working conditions of such workers have caused them to be viewed as a threat to domestic American workers. Some have argued that foreign guest workers compete unfairly with U.S. workers — both in terms of compensation that they are willing to accept and by making it somewhat more difficult for domestic workers to organize and to bargain with management. To mitigate any “adverse effect”for the domestic workforce, a system of wage floors was developed that applies, variously, both to alien and citizen workers: i.e., the adverse effect wage rate (AEWR). This report deals with one element of immigration (i.e., namely the H-2A workers). It introduces the adverse effect wage rate, it examines the concerns out of which it grew, and it explains at least some of the problems that have been encountered in giving it effect.