Objective: The aims of the present thesis were to explore the relationship between emotional self-regulation and peer relations of children with social and emotional behavioural difficulties (SEBD), and to describe the development and initial evaluation of CALM KIDS, an emotional self-regulatory intervention designed to enhance the development of regulation skills and increase peer awareness and understanding of social and emotional behavioural difficulties in the classroom . Method: The study was comprised of two phases. In Phase One, 70 children aged 8 to 1 2 years (M age= 9.93 years, SD= 1 .48; 48 males; 22 females) from 1 Catholic and 7 State primary schools across Brisbane participated in a cross-sectional study assessing their emotional, social, and behavioural skills of participants and whether these skills were positively or negatively associated with peer relations. In Phase Two, 60 children aged 8 to 1 2 years (M age= 9.91 years, SD= 1 .49; 4 1 males; 1 9 females) were selected from the Phase One participants to partake in a pilot intervention trial of a classroom-based emotional regulation program. Participants were randomly assigned to either intervention (n= 29) or control (n= 31 ) groups. Participants were assessed at pre-treatment and post-treatment through naturalistic observations, teacher monitoring, and self-monitoring. Results: For Phase One, children with SEBD were found to exhibit greater difficulties with social and academic competence, and exhibited higher rates of inattentiveness, hyperactivity, impulsivity and overall problem behaviours compared to the published norms reported for the standardized tests. Differences were also found in examinations of gender and formal verses no diagnosis. Females were found to exhibit greater rates of parent reported hyperactivity, and parent and teacher reported overall ADHD behaviour, higher emotional intensity, and less cooperation and assertion, than males. Children with a formal diagnosis were rated higher in oppositional behaviour than children without a formal diagnosis. Children formally diagnosed were also found to display lower levels of responsibility, self-control and social skills, and greater difficulties with externalizing, hyperactive and overall problem behaviours, according to parents. Overall, for children with SEBD, a significant association was found between negative emotional intensity and negative peer ratings. For Phase Two, at pre-intervention, no significant differences were found between intervention and control participants on observed behaviours. Post-intervention analysis revealed a significant improvement for the intervention group on observed behaviours across inter-observer, teacher, and self-reported monitoring from Time 1 to Time 2. Conclusion: The goal of this research was to explore the relationship between peer relations and self-regulatory capacities in children with SEBD, and to design and implement an effective self-regulatory intervention for use with children experiencing social, emotional and behavioural difficulties in the classroom. Preliminary results are promising, although further work is required to enhance classroom-based interventions.