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 which describes the decommissioning process and summarizes the current status of all decommissioning activities including the decommissioning of complex decommissioning sites, commercial reactors, research and test reactors, uranium mill tailings facilities, and fuel cycle facilities. In addition, this report discusses accomplishments in the decommissioning program since publication of the 2003 annual report (SECY-03-0161), and it identifies the key decommissioning program issues which the staff will address in fiscal year (FY) 2005.