The aims of this study were to administer an assessment measure that would identify prosocial children, bullies and their victims, and to examine the underlying structure of children's perceptions of peer social behaviour in these three groups. Three versions (peer nomination, self and teacher rating) of a newly developed child social behaviour questionnaire (CSBQ) were completed by children (aged 9/10 years, n=321) and their teachers in 14 Scottish primary schools. The CSBQ is distinguished from other extant measures by its joint focus on both prosocial and antisocial child behaviours, and by its use of concrete and empirically derived items. In conjunction with sociometric data, which was also elicited from the children, the CSBQ yielded scores on 12 behavioural dimensions. Based upon the peer nomination data, a set of rigorous criteria, capable of reliably identifying children in the three groups, was developed to take account of varying peer nomination practices within and between schools. Factor analysis of the 12 measures yielded four factors (two antisocial factors, a prosocial factor and a victim factor) which accounted for 71% of the variance, and which offer further insight into the organisation of children's perceptions of social behaviour. Gender differences in peer nomination patterns and comparisons between the different informant groups are discussed in relation to previous work.