This report presents an overview of biometric identification technology with particular attention to its potential use to improve the integrity of the FSP. It briefly describes some of the major technologies, summarizes their capabilities, gives examples of applications, and discusses issues that should be considered in evaluating biometric identification technology. It pays particular attention to applications of the technology to the FSP, or to other welfare programs. Although it describes several specific biometric identification technologies, it focuses on finger imaging, which has been the primary technology used in social service programs. A companion report describes the efforts of nine States that have incorporated or plan to incorporate biometric technology in their social service programs, and discusses the cost and effectiveness of these programs, as well as the reactions to them by the client population.