Yes / The Ad Hoc Group (AHG) of the States Parties to the Biological and Toxin Weapons Convention (BTWC) have touched from time to time on the question of the organisation needed to implement the legally binding instrument being negotiated to strengthen the BTWC. Now that the work of the AHG has intensified with the fleshing out of a rolling text for the legally binding instrument, the nature of the organisation is receiving more and more attention as its size and cost are likely to influence the nature and effectiveness of the regime developed by the AHG. This Briefing Paper considers what can be learned from existing relevant organisations, notably the World Health Organisation (WHO) and its counterparts for animal and plant diseases (OIE and FAO), the United Nations Special Commission (UNSCOM) on Iraq and the Organization for the Prohibition of Chemical Weapons (OPCW). The developments thus far in the AHG deliberations are then addressed and some estimates are made for the optimum size and cost of a BTWC rganisation. It is emphasised that these estimates are necessarily broad as the actual size of the BTWC Organization will depend on the precise functions and responsibilities that it is given.