Advances in modern biotechnology may have a significant impact on how biological weapons are acquired, produced, and delivered. Of the three major components that constitute a biological weapon—agent payload, munition, and dispersal mechanism—the techniques of modern biotechnology have most applications for agents. Techniques that may be applicable to the weaponization of pathogens and toxins include genetic engineering, DNA technologies, protein engineering, functional genomics, artificial viruses, and systems biology. These techniques might be applied to enhance one or more of the five characteristics or traits of microorganisms and toxins considered important for weaponization: hardiness, resistance, infectivity, pathogenicity, and detection avoidance. However, although the barriers to applying the advanced biotechnologies for nefarious purposes continue to drop, it must be realized that substantial expertise is required to perform R&D to achieve complicated weapons objectives; expertise that is not available by far to most terrorist groups.