Although prohibited by international treaties since the Hague Declaration of 1899 and the Hague Convention of 1907, chemical warfare (CW) agents have been used in a number of conflicts during the 20th century. The best known large scale uses were by both sides during World War 1. Significant quantities were also used, for example, by Imperial Japan in Manchuria and by Italy in Abyssinia (Ethiopia), both in the 1930s. These and other uses are well documented.¹  The entry into force of the Chemical Weapons Convention (CWC)²  in 1997 gave impetus to the elimination of chemical weapons, but possible possession by the few countries that have not signed the CWC and terrorist organisations remains of concern. Recent confirmed uses of the organophosphorus nerve agent sarin in Syria demonstrated the importance of maintaining the capability for verification of exposure to CW agents for diagnostic and forensic purposes.³  Analysis of environmental samples, such as soil, water and munition fragments, for detection of CW agents and their degradation products is well established.⁴  In conflict zones it is often not possible to collect suitable environmental samples and in such cases the collection of biomedical samples, usually blood and urine, from escaped or evacuated casualties is of great importance. The Organisation for the Prohibition of Chemical Weapons (OPCW), which administers the CWC, is in the process of setting up a system of designated laboratories for analysis of biomedical samples. Confidence building exercises held as part of this process have already resulted in significant capability increases in laboratories worldwide. These laboratories will complement the existing designated laboratories for the analysis of environmental samples.