Sources of sibling conflict included teasing, name calling, treatment of possessions, and jealousy. The modes of relating in agonistic interactions (e.g., teasing, name calling) were similar regardless of whether subjects were victims or perpetrators. Of subjects, 88 percent of males and 94 percent of females reported being victims of sibling physical violence, and 85 percent of males and 96 percent of females reported being perpetrators of physical violence in the previous 12 months. The most frequent violent behaviors were shoving, kicking, hitting, and throwing objects at the sibling. Results suggest that sibling conflicts are the most prevalent form of family violence, and that males and females engage in these conflicts to a similar extent. 31 references.