In sub-Saharan Africa, adolescent girls are three to four times more likely than adolescent boys to be living with HIV/AIDS. A literature review revealed only four studies that had examined HIV vulnerability from the perspective of community members. None of the studies focused specifically on adolescent girls. To fill this gap, in 2008 12 focus group discussions were held in selected peri-urban and rural sites in Botswana, 12 in Malawi, and 11 in Mozambique to identify factors that render girls vulnerable to HIV infection from the community members' perspective. The preponderance of comments identified structural factors--insufficient economic, educational, socio-cultural, and legal support for adolescent girls--as the root causes of girls' vulnerability to HIV through exposure to unprotected sexual relationships, primarily relationships that are transactional and age-disparate. Community members explicitly called for policies and interventions to strengthen cultural, economic, educational, and legal structures to protect girls, recognized community members' responsibility to take action, and requested programs to enhance adult-child communication, thus revealing an understanding that girls' vulnerability is multi-level and multi-faceted, so must be addressed through a comprehensive approach to HIV prevention.