Argonne National Laboratory in partnership with the US Department of Homeland Security (DHS) has developed a methodology to systematically evaluate the protection posture and vulnerability of critical infrastructure and key resources (CIKR). This vulnerability methodology is part of a larger effort by DHS called the Enhanced Critical Infrastructure Protection Programme, which seeks to mitigate vulnerabilities, enhance relationships, and improve information sharing between public and private entities. This methodology was constructed to be used in all CIKR sectors and to provide useful results to owners and operators of US facilities. The vulnerability index is also being used to assist DHS in analysing sector and subsector vulnerabilities, to identify potential ways to reduce vulnerabilities, and to assist in preparing sector risk estimates. The owner/operator also receives an analysis of the data collected for a specific asset, which gives an indication of the asset’s strengths and weaknesses with regard to security.