[영문]This article reviews the experience of some key low-, middle- and high-income countries that have successfully extended social security coverage or are in the process of doing so. It shows that a strong and competent State is a first requirement for the extension of social security. It also examines a variety of coverage indicators that can help national and international policymakers to focus their efforts on the extension of social security. Finally, it documents the growing use of tax-financed social pensions, and discusses some policy issues with regard to the link between tax-financed and contributory social security schemes.