Given the historical evidence, and the characteristics of biological weapons, it appears unlikely that terrorists will use these weapons to produce mass casualties. Yet this terrorist threat will continue to be a concern while many countries still have bioweapon programmes, with advances in genetic engineering, and while determinants of terrorism persist around the world (eg, unresolved conflicts, poverty, inequality and environmental degradation). Terrorist use of smallpox, pneumonic plague and genetically engineered pathogens in the Northern Hemisphere could lead to imported cases reaching New Zealand and some risk of ongoing disease outbreaks. However, a range of disease control measures are available that could substantially limit the size of any resulting outbreaks. The risk of terrorist use of bioweapons needs to be considered in the context of the more important risk of pandemic influenza on New Zealand, the many thousands of preventable deaths in each year in this country (eg, from smoking and physical inactivity), and the current epidemic of meningococcal disease. Nevertheless, attention needs to be given to the primary prevention of terrorism and to preparatory measures that improve the country's public health infrastructure.