Dangerous pathogens not only pose severe threats to human, plant, and animal health, but can also be used for ill-intended purposes. Such pathogens are listed as Select Agents and Toxins (SAs). The 2001 anthrax letter attacks prompted the creation of new regulations to increase security for research with dangerous pathogens. Are these measures adequate? This report evaluates the physical security of SA laboratories and the personnel reliability measures designed to ensure the trustworthiness of those with access to SAs. The book offers guiding principles and recommends changes to minimize security risks and facilitate research productivity.