Duck’s slightly paraphrased observation has particular relevance to the relational foundation of cross-sex friendships. From a life-cycle perspective, the cross-sex friendships an individual forms or fails to form during early childhood have long-lasting implications for similar friendships throughout life. Those early friendships provide the child with a cross-sex friendship schematic blueprint that guides behavior in subsequent cross-sex friendships. One of the major contentions of this chapter and book is that successful formation of cross-sex friendships early in life increases the probability of having those relationships and their attendant advantages in later stages of the life cycle. Additionally, cross-sex friendships and the quality of those relationships in early childhood impact socially constructed views of self. In turn, those views influence attitudes about cross-sex friendships and behavior in those relationships. These contentions and others are explicated and documented in the four sections of this chapter. The first three sections develop the central themes of the book and relate each theme to early childhood. In the final section I offer some concluding observations about cross-sex friendships in early childhood.