This report contains the most current and comprehensive statistics on children orphaned by AIDS and other causes (appendix 1). Unlike previous editions of Children on the Brink, which included data for children under age 15, this edition provides data for children under age 18. This change brings the statistics in line with the international definition of childhood. It also recognizes that orphans and vulnerable children are not necessarily young children and that problems caused by orphaning extend well beyond age 15. The available data in fact suggest that adolescents make up the majority of orphans in all countries. As another new feature, this report also includes estimates of the number of children who became orphans in the last year.The methodology explaining how all estimates are calculated is described in appendix 2. This edition of Children on the Brink also examines the changing developmental needs of orphans and other children made vulnerable by HIV/AIDS as they progress through childhood. From infancy through age 17, a child passes through a number of life-cycle stages. HIV starts to affect a child early in a parent's illness, and its impact continues through the course of the illness and throughout the child's development after the parent's death.Children who are deprived of the guidance and protection of their primary caregivers are more vulnerable to health risks, violence, exploitation, and discrimination. Policymakers, leaders and practitioners in public health and other development sectors, and communities and families need to provide care and support to orphans (from all causes) and children made vulnerable by HIV/AIDS with an understanding of their stages of development and changing needs.