Under the Department of Homeland Security (DHS) Appropriations Act of 2007, DHS has the authority and funding to regulate security at facilities storing chemicals considered to be high-risk (P. L. 109-295, Section 550). This article discusses the Department's efforts to enhance the security of facilities that store chemicals that could be stolen or used by terrorists to inflict mass casualties. It also details the steps necessary to comply with federal regulations once a facility has determined they are storing Chemicals of Interest (COI) as defined by Appendix A of the Chemical Facility Anti-Terrorism Standards (CFATS) Final Rule. The rule expects facilities to develop a layered approach to security measures, with a written plan that describes each component and how it--in combination with other security measures-- will address the identified Risk-Based Performance Standards (RBPS). The owner/operator of the facility will also be required to maintain and update the Site Security Plan (SSP) on a regular basis. Facilities covered by the rule have flexibility in determining the methods they will use to meet the requirements. DHS will assess the adequacy of those security measures by reviewing the written SSP and conducting site visits.