The federal government is the largest employer in the United States, and the Federal Employees Health Benefits (FEHB) Program is the largest employer-sponsored health insurance program in the country. It provides more than $40 billion in health care benefits annually. This first chapter of this book provides a general overview of FEHB. It describes the structure of FEHB, including eligibility for the program and coverage options available to enrollees, as well as premiums, benefits and cost sharing, and general financing of FEHB. The chapter also describes the role of the Office of Personnel Management (OPM) in administering the program. The second chapter discusses the Patient Protection and Affordable Care Act (ACA) which generally specifies that the only health plans that the federal government may make available to Members and certain congressional staff are either created under ACA or offered through an exchange. The chapter summarizes the provisions of the final rule made me OPM which amends FEHBP eligibility regulations, and describes how it affects current and retired Members and congressional staff. The third chapter in this book provides historical and background information that helps explain how FEHBP has evolved into the program it is today. The fourth and final chapter describes oversight of fraud and abuse programs by OPM's contracting office, and the OPM contracting office's approach to measuring the effectiveness of FEHBP carriers' fraud and abuse programs.