This is a brief based on a background paper prepared for the WHO/UNFPA/Population Council Technical Consultation on Married Adolescents held in Geneva, Switzerland, 9-12 December 2003. Over the next decade in developing countries, more than 100 million girls under the age of 18, "children" as defined by the Convention on the Rights of the Child, will be married. In countries with HIV epidemics, these girls, most of whom live in Africa and Asia, are at substantial risk for HIV/AIDS infection. The Consultation brought together experts from the United Nations, donors, and nongovernmental agencies to consider the evidence regarding married adolescent girls' reproductive health, vulnerability to HIV infection, social and economic disadvantage, and rights. The relationships to major policy initiatives--including safe motherhood, HIV, adolescent sexual and reproductive health, and reproductive rights--were explored, and emerging findings from the still relatively rare programmes that are directed at this population were discussed.