The International Institute for Sustainable Development’s Global Subsidies Initiative (GSI) was launched at the end of 2005, just prior to the WTO Ministerial Conference in Hong Kong, China. Delegates to the WTO meeting had gathered from around the world to discuss a wide range of issues being negotiated as part of the Doha Round of multilateral trade talks, but topmost on their minds were subsidies. What to do about agricultural subsidies, and market access (tariff and non-tariff barriers), was, as always, the make-or-break issue. But also on the table were various proposals for sharply reducing subsidies to fisheries, and perhaps eventually developing new “disciplines” on subsidies affecting trade in services. Yet despite the fact that subsidies have become a central issue on the international agenda, the available information on subsidies is both highly dispersed and highly technical. While many valuable contributions have been made over the years to the literature of subsidies, most have been in the form of scholarly articles or books written by and for economists or trade experts. These tended to be either monograph focused on the magnitude of subsidies or their effects or popular diatribes aimed at ridiculing subsidies in particular countries. For anybody approaching the subject anew, they would face a steep learning curve indeed. Subsidies are not difficult to understand, but because the terms and definitions used by individual policy communities differ, confusion is virtually guaranteed. What was needed, in brief, was a book that covered all the issues related to subsidies, yet was short enough and accessible enough to attain a wide readership. In producing this Subsidy Primer we are attempting to fulfill that need.