Over the past decade, there has been growing recognition of the importance of social protection to respond to a range of challenges faced by developing countries, including food insecurity, chronic poverty and the HIV pandemic. HIV and AIDS can push people and households into poverty, in part by reducing household labour capacity and increasing medical expenses. In some cases, HIV-related stigma and discrimination marginalises people living with HIV (PLHIV) and households affected by the virus and excludes them from essential services. Despite increased access to life-saving treatment, HIV and AIDS can increase individual and household vulnerabilities - hampering governments’ effort to meet the Millennium Development Goals. In the face of rising HIV prevalence rates and the aftershocks of the recent economic crisis, few developing countries outside of Latin America have national social protection systems and large scale coverage. Social protection systems are especially limited in sub-Saharan Africa, with the notable exception of a few southern African countries. While many existing social protection schemes were not set up with HIV as a primary focus, their potential to contribute to a comprehensive HIV response is increasingly recognised. The UNAIDS Business Case on social protection shows how HIV-sensitive social protection can reduce vulnerability to HIV infection, improve and extend the lives of people living with HIV, and support individuals and households. Under the Outcome Framework 2009–2011, UNAIDS will focus its efforts on achieving results in nine priority areas. Among these is the commitment to “enhance social protection for people affected by HIV”. Achieving social protection for people and households affected by HIV is a critical step towards the realisation of universal access to prevention, treatment, care and support. The business case explains why this is the case, what needs to be done, and the role of UNAIDS in this endeavour.