This special report presents a prototype vulnerability assessment methodology developed for chemical facilities to use to identify and assess potential security threats, risks, and vulnerabilities. The National Institute of Justice developed the vulnerability assessment methodology as a practical method to assess the security of chemical facilities within the United States. The vulnerability assessment methodology is designed to guide the chemical facility industry in making security improvements at chemical facilities. This vulnerability assessment methodology is therefore focused primarily on terrorist or criminal actions that could have significant national impact (e.g., through the loss of chemicals vital to the national defense or economy) or cause releases of hazardous chemicals that would compromise integrity of the facility, cause serious injuries or fatalities among facility employees, contaminate adjoining areas, and cause injuries or fatalities among adjoining populations. Thus the use of this vulnerability assessment methodology should be limited to these areas. It addresses primarily physical security at fixed sites and does not address cyber and transportation security issues.