The study of peers who dislike one another, termed mutual antipathies, is being recognized as an important aspect of a child's social world. An overview of this area and a review of the literature concerning mutual antipathies is provided. Particularly of interest is the type of mutual antipathy known as an "enemy" relationship, and special focus is given to the process of identifying children's enemies in empirical research; the factors involved in the formation and maintenance of enemy relationships; and the value of enemy relationships in strengthening other peer relationships and developing an integrated sense of self. (Contains 1 figure.)