This article reviews the psychiatric aspects of hyperthyroidism. The psychosomatic theory in the aetiology of thyrotoxicosis is first reviewed in relation to pre-morbid personality and stress. The nature of hyperthyroidism is briefly analysed, as it has direct relevance to the integral psychiatric manifestations of the disorder. Psychiatric manifestations are then described: firstly, those that are an integral part of hyperthyroidism and; secondly, those which have been reported to occur in association with hyperthyroidism. The psychosocial impact of the disease is also considered. There follows a discussion of the antecedents of psychiatric disorder in relation to mediating psychological and biological factors. The article reviews past and present evidence concerning the nature of the association between hyperthyroidism and other psychiatric disorders. Course and outcome of psychiatric disorder in hyperthyroidism are reviewed and, lastly, an appraisal is made of implications for management.