Studies into school bullying have typically examined physical or verbal acts of aggression. More recently, consideration has been given to another form of bullying which can be as damaging to its victims, namely, indirect, relational, and social aggression. These forms of aggression are intended to inflict harm by manipulating social relationships, spreading rumours, and excluding others from the group. Although these terms are superficially similar, particularly with respect to the types of manipulative acts they involve, there is disagreement over which construct is most useful for describing these manipulative forms of behaviour. The aim of the present study was to develop a measure of relational bullying which integrates behaviours from all three constructs. In addition, the study investigated possible relationships between relational bullying and depression, anxiety, and externalising behaviours in adolescents. These effects were examined for victims and bullies of relational bullying, as well as students who witness and intervene in relational bullying.