This report provides a comprehensive overview of the U.S. Nuclear Regulatory Commission's (NRC's) decommissioning program. Its purpose is to provide a stand-alone reference document that describes the decommissioning process and summarizes the status of decommissioning activities, under NRC jurisdiction, through September 30, 2006. This includes the decommissioning of complex decommissioning sites, commercial reactors, research and test reactors, uranium recovery facilities, and fuel cycle facilities. In addition, this report discusses accomplishments of the decommissioning program in fiscal year (FY) 2006; identifies the key decommissioning program issues that the staff will address in FY 2007; and provides information Agreement States have supplied on decommissioning in their States.