This is the first in a series of publications produced by the Child and Youth Studies Group at The Open University, United Kingdom, with the support of the Bernard van Leer Foundation. The series provides accessible and clear reviews of the best and most recent available research, information and analysis on key policy issues, offering clear messages on core policy topics and questions. The subject of this issue is attachment relationships between infants and caregivers, what influences them and how they impact on an infant's development. NB: pdf also available in Hungarian.