Many potential chemical, biological, radiological, and nuclear (CBRN) terrorism agents lack available medical countermeasures. In 2003, President Bush proposed Project BioShield to address this need. The Project BioShield Act became law in July 2004 (P.L. 108-276). This law has three main provisions: (1) relaxing regulatory requirements for some CBRN terrorism-related spending, including hiring and awarding research grants; (2) guaranteeing a federal government market for new CBRN medical countermeasures; and (3) permitting emergency use of unapproved countermeasures. The Department of Health and Human Services (HHS) has used each of these authorities. The HHS used expedited review authorities to approve 5 contracts and 47 grants related to CBRN countermeasure research and development. The HHS used the authority to guarantee a government market to obligate approximately $2 billion to acquire countermeasures against anthrax, botulism, radiation, and smallpox. The HHS has also employed the emergency use authority several times, including allowing young children with H1N1 "swine" influenza to receive specific antiviral drugs. The Department of Homeland Security (DHS) Appropriations Act, 2004 (P.L. 108-90) advance-appropriated $5.593 billion for FY2004 to FY2013 for CBRN countermeasures acquisition through Project BioShield. Subsequent Congresses have rescinded or transferred to other accounts approximately 19% of the advance appropriation. In FY2004 and FY2005, Congress removed a total of approximately $25 million from this account through rescissions included in the Consolidated Appropriations Act, 2004 (P.L. 108-199) and the Consolidated Appropriations Act, 2005 (P.L. 108-447). In the Omnibus Appropriations Act, 2009 (P.L. 111-8), Congress transferred an additional $412 million to support countermeasure advanced research and development and pandemic influenza preparedness and response. The Consolidated Appropriations Act, 2010 (P.L. 111-117) transferred $609 million to support countermeasure basic and advanced research and countermeasure development. P.L. 111-117 also transferred the BioShield appropriation account from DHS to HHS. Since passing the Project BioShield Act, subsequent Congresses have considered additional measures to further encourage countermeasure development. The 109th Congress passed the Pandemic and All-Hazard Preparedness Act (P.L. 109-417) which created the Biomedical Advanced Research and Development Authority (BARDA) in HHS. Amongst other duties, this office oversees all of HHS' Project BioShield activities. The Pandemic and All-Hazard Preparedness Act also modified the Project BioShield procurement process. Questions remain regarding whether these changes have sufficiently improved countermeasure development and procurement. The 111th Congress faces several challenging policy issues. Primary among them is assessing whether Project BioShield is successfully encouraging medical countermeasure development. A second issue is whether to allow additional diversions of the Project BioShield advance appropriation, a key element of the government's market guarantee, to support other activities. A third is whether to broaden Project BioShield's mandate beyond CBRN countermeasures in the face of other threats, such as pandemic influenza.