The IRCA forbids employers' hiring of illegal aliens and establishes a public information and regulatory apparatus to help employers comply with the law and detect and punish violators. The study is based on extensive interviews and other data collected between February 1988 and November 1989 in Washington, D.C.; the four regional offices of the Immigration and Naturalization Service (INS), four State capitals, and eight localities. The study identifies four major challenges to the implementers of the law, notably the INS: establishing the legitimacy of sanctions as a new set of employment regulations, satisfying the legal requirements that attach to business regulation, adapting the INS to monitor and sanction employers, and regulating a vast economic process with limited investigative and enforcement resources. These challenges form the framework for evaluating IRCA's implementation. The study concludes that the implementers have essentially met the challenges of IRCA's first 3 years; however, the arrangements adequate for the startup phase are inadequate for a more mature program. The study recommends ways to strengthen the implementation of employer sanctions. Chapter notes.