Relational aggression is common among girls. It can be distressing for the victim and may not always be recognised as a form of bullying. This paper evaluates a school–based intervention designed to help girls understand relational bullying. Girls from a single-sex school completed a two-stage evaluation of the intervention. Students showed greater awareness of relational bullying after the intervention and indicated that it would influence them to change their behaviour. At follow-up, retention of knowledge was good. Students reported greater self-monitoring of behaviour and less exclusivity. While this is encouraging, we cannot conclude that all negative behaviours ceased. Implications and limitations of this study are discussed. Copyright © 2010 John Wiley & Sons, Ltd.