The biological warfare capabilities of state and non-state actors continue to grow worldwide, both in sophistication and breadth. More than a dozen nations, including Iraq, Iran, Libya, Syria and North Korea, are either actively pursuing or possess biological weapons for use against their enemies. There is also a heightened awareness of the use of such agents by terrorist groups, a possibly deleterious side-effect of an increased awareness by the general public. This paper looks at the growing threat of the use of biological agents by both national programmes and non-state actors, the possible agents which might be considered for use, and the potential role that vaccine development may have in protecting both military and civilian populations against biological weapons attacks in the future.