Asperger's syndrome is a relatively newly diagnosed developmental disorder within the autistic spectrum. Children and adults with Asperger's syndrome have an intellectual ability within the normal range but due to their unusual profile of cognitive, social and emotional abilities are vulnerable to the development of a secondary mood disorder. This paper provides an explanation of the abilities associated with Asperger's syndrome, and modifications to cognitive behaviour therapy (CBT) for this very unusual client group. In particular, the paper emphasises the importance of affective education for this clinical population and describes a new strategy used in cognitive restructuring, namely, the emotional toolbox. The paper concludes with a brief description of a current evaluation study of the effectiveness of CBT to treat anxiety and anger in children who have Asperger's syndrome. However, the strategies described in this paper can also be used with adults with Asperger's syndrome and applied to other clinical populations.