It is recognized that IUU fishing brings about negative impacts on the economic, social and ecological attributes of fisheries that affect food security. Specifically, IUU fishing has contributed to the reduction in food supply, lost livelihoods and state revenues, diminishing fish stocks, and damaging ecosystems, with the most devastating effects concentrated in developing countries due to their greater vulnerability. These illegal activities form a complex web – from illegal fishing activities to illegal trade, and finally to persistent catching from unsustainably fished stocks with the underlying objective of getting high profit from illegally caught fish. Members of FAO Committee on Fisheries have agreed on the need of Good Practice Guidelines for national fisheries authority(ies) to prevent, deter and eliminate illegal, unreported and unregulated (IUU) fishing through the effective implementation of flag State responsibilities. The Guidelines are wide-ranging and address the purpose and principles, the scope of application, performance assessment criteria, cooperation between States. They are expected to provide a valuable tool for strengthening compliance by flag States with their international duties and obligations regarding the flagging and control of fishing vessels.