How do personal networks evolve and what roles do they play for parents, and for the development of children? Can these ties with relatives, neighbors, 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. The authors document and compare the roles of network member players, the ways that networks change over time, and the impact of different network resources on developing individuals. The impacts on parent network participation in a community-based family support program are examined, and a more general discussion of how public policies might strengthen access to informal social supporters is also provided.