This paper reviews the state of fishery resources of tuna and tuna-like species on a global scale, focusing on those most important commercially, i.e. the so-called principal market tuna species. These are classified as tropical tunas (skipjack, yellowfin and bigeye) and temperate tunas (albacore and bluefin [Atlantic, Pacific and southern]). For each tuna and tuna-like species, the document provides: taxonomic and other basic biological information; the development and expansion of the fishery; catch trends; institutional frameworks for regional cooperation in fisheries research, particularly stock assessment; procedures and input information for stock assessment; the status of the stocks; potential improvements in knowledge of the status of the stocks; and the future outlook for this status and catches.