A convention prohibiting the development, production, acquisition, stockpiling, retention, transfer and use of chemical weapons has for quite some time been on the agenda of arms control negotiations. Chemical weapons include toxic chemicals, munitions and related equipment. International verification of compliance with a chemical weapons convention would apply to four main areas: declaration of possession; elimination; development, acquisition, transfer, production and non-production; and use. Chemical weapons are a particularly difficult field in which to verify activities because so-called national technical means are unable to verify what is happening inside a building or what agent is contained within a weapon. The degree of verifiability depends on various activities which require different technical means. A multilateral authority will be needed to verify compliance with a convention on chemical weapons. Such an international verification body should be equipped with qualified experts and advanced verification technology.