For the most part, separate research traditions have developed to study children ' s relationships with parents and peers. The organization and format of this handbook refl ect these separate and distinct literatures. Studies of children ' s interactions with their parents have focused on attachment security (see Chapter 17 ), parenting practices (see Chapter 18 ), and variations associated with demographic and cultural factors (see Chapters 8 and 9 ). As a quick perusal of these chapters reveals, a central issue for many researchers is identifying the effects of children ' s experiences with their parents on a host of social and emotional outcomes including mental health, adjustment, empathy, and prosocial behaviors. Other researchers have focused on children ' s relationships with their peers and studied areas such as peer acceptance and rejection (see Chapter 21 ), friendship (see Chapter 25 ), and peer group interaction (see Chapter 23 ) as socializing infl uences on child developmental outcomes. As a review of the four chapters in the " Peer Group " part of this handbook clearly illustrates, this corpus of work is also large.The purpose of the current chapter is to consider the smaller but important body of literature that examines the role of both parents and peers on child development. We consider fi ve interrelated issues: (a) the infl uence of parent -child relationships on children ' s interactions and relationships with their peers, (b) the infl uence of peer experiences on children ' s interactions and relationships with their parents, (c) additive or cumulative effects of parents and peers on social and cognitive outcomes, (d) interactive or synergistic effects of parents and peers on child developmental outcomes, and fi nally