The focus of this thesis was the evaluation of a treatment to help people who have a learning disability to develop socially appropriate ways of expressing anger. The inability to cope with anger has prevented some people from living an ordinary life in the community. A cognitive behavioural treatment to help people to cope with anger was developed by Novaco (1983b). The aim of the present studies was to examine whether a modification of the treatment developed by Novaco could prove beneficial for a population who have a learning disability. A set of criteria for improvement were devised to operationalise improvement in terms of clinically, as well as statistically significant change. In study 1, twelve people who have a learning disability were assessed on one self report measure and four measures completed by staff; at baseline, at the end of each stage of treatment and follow up. The subjects received approximately fifty weeks of treatment. As the follow up scores met the majority of the criteria for improvement, it was inferred that the subjects had benefited from treatment. A number of methodological modifications were suggested. In study 2, five subjects were assessed on four self report and three staff completed assessments. The four stages of treatment (self monitoring, information giving, relaxation training and problem solving) lasted 27-37 weeks. Four of the five subjects benefited from treatment as their follow up scores met the criteria for improvement. The results allowed cautious optimism about the efficacy of cognitive behavioural techniques and the use of self report measures for people who have a learning disability, who are verbal. The value of embedding this focussed treatment within a broader therapeutic framework, to encompass a wider range of emotions and strategies to cope with stress was discussed.