FAOs Japan-funded project "Management of tuna fishing capacity: conservation and socio-economics" was formulated with the aim of improving the management of tuna fisheries on a global scale. Its immediate objectives are to provide the technical information necessary for the management of tuna fishing capacity and to identify and resolve the associated technical problems on a global scale, taking into account conservation and socio-economic issues. This publication includes papers on the studies that were considered high priority by the project and its Technical Advisory Committee (TAC) at its first meeting (Rome, Italy, 14-16 April 2003). Earlier versions of papers on these studies were presented to the second meeting of the TAC (Madrid, Spain, 15-18 March 2004), where they were critically discussed. The studies were subsequently peer reviewed, revised and edited.