Merriam et al. (1988) asserted that Alzheimer’s disease (AD) is ‘the most widely encountered cause of psychiatric pathology associated with a specic neuropathological substrate’. is is consistent with phenomenological studies and literature reviews, which generally converge on the conclusion that roughly 90% of patients with dementia will develop signicant behavioural problems at some point in their illness (Tariot and Blazina, 1993). e ‘behavioural and psychological signs and symptoms of dementia’ (Finkel et al., 1996) do not typically meet criteria for discrete psychiatric disorders. ey do, however, tend to occur in clusters of signs and symptoms that may vary among patients and over time (Tariot and Blazina, 1993). Examples of these clusters are provided in Table 25.1, based upon a review of published studies regarding psychopathological changes in dementia that was performed in 1993. With experience, these clusters of signs and symptoms can be both predicted and recognized, and can be used as guideposts in the selection of appropriate therapy.