Most attacks by terrorists have involved the use of conventional munitions including explosives. It is likely that explosives will remain the weapon of choice by terrorists, however, it is also possible that attacks in the future may involve chemical and biological agents. It would be irresponsible to ignore this possibility and governments need to plan for such an eventuality. Emergency and other professionals involved in dealing with the aftermath of the release of a chemical or a biological agent face many challenges including detecting what has been released, determining who might have been exposed and what has been contaminated as well as how to clean up afterwards. All these activities require the use of equipment, measurement approaches and protocols which the scientific community could help develop. A UK Royal Society working group was convened in 2003-4 to consider these issues and this paper discusses its recommendations.