This chapter analyzes the inspector general (IG) concept including why Offices of Inspector General were established, what they do, how they evolved during the last 30 years since their establishment by statute, what changed, and what influenced/challenged IGs effectiveness. It addresses corruption, fraud, waste, and abuse, identifying what they involve in regard to IGs interventions against fraud and corruption within federal programs and operations. The phenomenon of corruption has been a subject of study for a number of international organizations such as the Organization of American States (OAS), the Organization for Economic Cooperation and Development (OECD), the United Nations (UN), and the World Bank (WB). The chapter describes the principal activities that IGs perform in order to achieve their mission. It analyzes main provisions related to functions of the inspector general, investigation of whistle blowing, IGs independence, reporting requirements, and coordination with other federal agencies. Finally, it addresses main issues related to components of IG effectiveness identified by the theory.