The relationship between HIV and mobility is widely recognized. While mobility and migration are not risk factors for HIV by themselves, the often harsh, unsafe and isolated conditions surrounding the mobility process can give rise to behaviours strongly associated with increased vulnerability to HIV, while also posing barriers to access to HIV prevention, treatment and care. Recent research has explored these dynamics in the Red Sea ports and adjacent transport corridors and found that cross-border mobile populations interact in spaces shaped by high HIV vulnerability throughout the Horn of Africa and Arab Peninsula. This reality has the potential to drive the propogation of the epidemic in the region, and undermine efforts made towards universal access and the achievement of the Millennium Development Goals. The current report builds directly on the 2010 UNAIDS report, Mobility, Migration and HIV Vulnerability of Populations along the Ports of the Red Sea and the Gulf of Aden: Mobility, Migration and HIV Vulnerability of Populations along the Ports of the Red Sea and Gulf of Aden Synthesis, desk review and exploratory studies report, to provide a literature review and updated situational analysis of the HIV vulnerability factors experienced by key populations in Djibouti, Egypt, Eritrea, Ethiopia, Somalia, Sudan and Yemen, to present a response analysis for activities completed under this initiative in 2011, and to consider lessons from programming experiences outside of the region.