[ABSTRACT] Social security in the Republic of Korea has developed rapidly in all three fields？social insurance, public assistance, and social services. Public expenditures have risen while coverage has gradually extended to become almost universal in some areas. However, public expenditures are still below those of other OECD countries, and the Korean social security system faces tough challenges ahead. Although Korea has developed an ever more elaborate social security system, successive governments have left major responsibility for protecting against risks to individuals, households, and the market. Until recently, social security and welfare goals were subordinate to economic growth. Social security became an important policy issue during the 1997？98 crisis, as unemployment soared. With unemployment came other social problems: rising poverty, family dissolution, homelessness, and child neglect. As a result, Korea acted to confront the urgent and overriding challenge of strengthening the social security system by earmarking higher budgets for the welfare system and reorganizing administrative structures. This chapter introduces the overall Korean social security system？which includes social insurance, public assistance, and social services？and its limitations. The chapter compares Korea？s social welfare expenditures and programs with those of other OECD countries, and concludes with a summary of the future social security challenges facing Korea.