Despite their high profile and potentially devastating consequences, bioterrorist acts are relatively unpredictable, rare, and thus far small-scale events. In contrast, biological invasions are occurring daily in the US and have significant impacts on human health, agriculture, infrastructure, and the environment, yet they receive far less attention and fewer resources. Scientists and the US government must work together to implement a comprehensive approach to biosecurity that addresses not only bioterrorism, but also the more common incursions of invasive alien species. This approach should also address the potential for the deliberate use of invasive alien species as agents of bioterrorism. To achieve these goals, it will be necessary for the relevant government institutions to acknowledge and include prevention, early detection, and rapid response to species incursions as central mission themes. In addition, the scientific community, industry, and the public must work together to ensure that the neces...