This chapter reviews the development and growth of the policy-analytic profession. Historically, government decision makers have often called upon those with expertise to assist them in reaching their decisions. This chapter, however, concerns a new professional class of advisors that began developing during the 1950s in the United States. This new profession assists policy makers in understanding better their alternatives and relevant considerations for choosing among them. From here, the chapter offers some perspective on the research to date that has attempted to assess the effects of the profession—a perspective that emphasizes some important differences across the many types of governmental settings that utilize policy analysis, and the methodological difficulties that assessment efforts confront.