How do personal networks evolve and what roles do they play for parents, and for the development of children? Can these ties with relatives, neighbours, and friends provide stability for family members during periods of disruption caused by divorce, unemployment, geographic dislocation or serious illness? How do networks change over time? To what extent are network members interchangeable; can unrelated friends take the place of close relatives? These are among the questions addressed in Extending Families, a ground-breaking study about how personal networks evolve, and what roles they play for parents and for the development of children. The volume is an outgrowth of a ten-year cooperative research effort carried out by the authors as part of the Comparative Ecology of Human Development Project at Cornell University. In this comprehensive and integrated volume, Moncrieff Cochran and his colleagues document and compare the roles network members play in the lives of African-American and Caucasian parents in the United States, and parents in Sweden, Wales and West Germany. They then go beyond those descriptive comparisons to consider, within a larger ecological framework, the ways that networks change over time, and the impact of different network resources on the perceptions and behaviour of developing individuals. The impacts on parents’ networks of participation in a community-based family support programme are examined, and a more general discussion of how public policies might strengthen access to informal social supporters is also provided. Moncrieff Cochran draws on this unique body of research in the concluding chapters of the volume to offer a new, integrated conception of how personal networks develop, and how they affect and are affected by development. In his foreword to this book, Urie Bronfenbrenner remarks that this conception provides the framework for a new approach to the scientific study of social networks and their implications for policy and practice’. Extending Families will be of special interest to family and urban sociologists, developmental and community psychologists, and other working in the areas of family policy, family studies, and human development.