Estimating the number of children in formal alternative care: Challenges and results – Given the relatively large body of literature documenting the adverse impacts of institutionalization on children’s developmental outcomes and well-being, it is essential that countries work towards reducing the number of children in alternative care (particularly institutional care), and, when possible, reunite children with their families. In order to do so, reliable estimates of the numbers of children living in such settings are essential. However, many countries still lack functional administrative systems for enumerating children living outside of family care. The purpose of this paper is to provide a snapshot of the availability and coverage of data on children living in residential and foster care from some 142 countries covering more than 80 per cent of the world’s children. Utilizing these country-level figures, it is estimated that approximately 2.7 million children between the ages of 0 and 17 years could be living in institutional care worldwide. Where possible, the article also presents regional estimates of the number of children living in residential and foster care.