From 1997 through 2007, the Horizons program conducted research to inform the care and support of children who had been orphaned and rendered vulnerable by acquired immunodeficiency syndrome in sub-Saharan Africa. Horizons conducted studies in Kenya, Malawi, Rwanda, South Africa, Uganda, Zambia, and Zimbabwe. Research included both diagnostic studies exploring the circumstances of families and communities affected by human immunodeficiency virus (HIV) and evaluations of pioneering intervention strategies. Interventions found to be supportive of families included succession planning for families with an HIV-positive parent, training and supporting youth as caregivers, and youth mentorship for child-headed households. Horizons researchers developed tools to assess the psychosocial well-being of children affected by HIV and outlined key ethical guidelines for conducting research among children. The design, implementation, and evaluation of community-based interventions for orphans and vulnerable children continue to be a key gap in the evidence base.