Much of the research involved field visits in 1982 and 1983 to welfare agencies in eight States: California, Illinois, Louisiana, Massachusetts, New Jersey, New Hampshire, Ohio, and Texas. Detailed cost-benefit analyses were conducted for four of the investigative programs believed to be most effective. After discussing the nature of fraud in public assistance programs and summarizing the data requirements that must be met before wage matching can be undertaken, the book recounts the origins and use of wage matching. The descriptive portion of the analysis discusses the basic elements in virtually all wage-matching operations. In presenting the cost-benefit analyses of wage matching, the book defines benefits and costs, identifies measurement problems, and reports on the case studies. Findings suggest that, when viewed from the government's perspective, benefits from wage matching in the four study sites outweigh costs by margins ranging from 56 to well over 100 percent. Recommendations for improved wage matching systems focus on administration, the prioritization of 'raw hits,' wage-matching data, preventing future overpayments, restitution of previous overpayments, and investigation. Appendixes describe wage matching operations in several sites and detail data and methods. 70-item bibliography.