The darker side of peer relations is subject that has been largely ignored by researchers. This volume begins the much-needed theoretical and empirically based explorations of the factors involved in the formation, maintenance, and impact of enemies and other mutual antipathies. Using diverse samples, the chapter authors provide an empirically based exposition of factors relevant to the formation and maintenance of these relations, as well as their developmental impact. Both distal (for example, attachment styles with parents, community violence exposure) and proximal (for example, perceptions of enemies' behavior, social structure of the peer group) factors related to inimical relations are explored, and the developmental sequelaw (for example, affective, behavioral, interpersonal) of having enemies are examined with concurrent and longitudinal designs.