The peptide hormones oxytocin and vasopressin have been implicated in a range of mammalian social behaviors including maternal care, pair bonding and affiliation. Oxytocin is of special relevance to female behavior because its effects are strongly modulated by estrogen. This article reviews animal and human research and is organised in terms of two research perspectives. The specific attachment model identifies oxytocin as orchestrating special bonds with offspring and mates, including the use of aggression in the protection of these relationships. The trait affiliation model considers oxytocin in relation to the trait of general social motivation that varies between and within species. Implications for understanding and researching the role of oxytocin in women's attachment, affiliation and aggression are discussed.