Current methods of assessing and treating aggression in children and adolescents with developmental disabilities were reviewed. While a number of measures have been developed to assess aggression in the general population, there are relatively few assessment methods for use with children and adolescents with developmental disabilities. In all, 54 studies on assessment and 62 on treatment were found. All of the assessment studies and 34 of the treatment studies met methodological criteria for this review. There were 22 assessment studies using checklists and 32 using behavioural observations. Of the treatment studies identified, 32 used behavioural interventions and two used pharmacological interventions. The most commonly used treatments were functional communication training and differential reinforcement of other behaviour. While there are still relatively few methodologically sound assessment and treatment studies, the number of viable publications is increasing.