Within the last 30 years, the genomes of thousands of organisms, from viruses, to bacteria, to humans, have been sequenced or partially sequenced and deposited in databases freely accessible to scientists around the world. This information is accelerating scientists’ ability to fight disease and make other medical advances, but policymakers must consider the possibility that the information could also be used for destructive purposes in acts of bioterrorism or war. Based in part on views from working biological scientists, the report concludes that current policies that allow scientists and the public unrestricted access to genome data on microbial pathogens should not be changed. Because access improves our ability to fight both bioterrorism and naturally occurring infectious diseases, security against bioterrorism is better served by policies that facilitate, not limit, the free flow of this information.