The 12th meeting of the Conference of Parties to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) took place in Santiago, Chile, from November 3 to November 15, 2002. During this meeting the Parties (signatories to CITES) voted to include all seahorses in Appendix II of the Convention, effective May 15, 2004. Effective implementation of the CITES listing will require that government authorities and other stakeholders be able to identify seahorse species that are utilized in international trade. This guide has been developed to help meet this need. The goal of the guide is to provide technically accurate information that is useful to specialists and non-specialists alike. This is no simple task as many species are similar in appearance and their identification can be challenging. The trade in seahorses involves both live and dead specimens. In some regions the live trade is the dominant pressure on seahorse populations, but the great majority of the seahorses in international trade are dried and destined for use in traditional medicine. This guide therefore has been designed with a bias towards the identification of dead specimens.