Oxytocin and vasopressin are highly conserved neuropeptides that play a key role in social attachment and affiliation, including parental care and pair-bonding. Oxytocin attenuates neural responses to aversive pictures and has been associated with reduced coupling of amygdala to brainstem regions involved in the fear response. Differential activation of the amygdala has been found to be associated with different genetic variants of the vasopressin receptor. There is growing evidence that oxytocin and vasopressin receptor variants are associated with individual differences in prosocial behavior. It is humbling that differences in complex human behaviors may be partially explicable on the basis of relatively simple neuropeptide systems. Nevertheless, such findings potentially allow for targeted interventions for a range of psychiatric disorders in which such systems play a role.