Dementing disorders are found most commonly in the elderly. However, the approaches derived from the diagnosis and management of these patients exemplify principles which can equally well be applied to the management of psychiatric disorders in younger patients. These principles include the process of syndromic diagnosis, the need for multi-dimensional assessment, the recognition of the interaction of biological and psycho-social factors in the etiology and treatment of psychiatric symptoms and the crucial role of the family in the management of patients with dementia. In this paper these principles are discussed.