 Alzheimers disease AD is the most common form of dementia and is characterized by both cognitive and behavioural symptoms Behavioural and Psychological Symptoms of Dementia; BPSD. To date, there are only modestly effective treatments for BPSD, and these treatments are associated with an increased risk of mortality in elderly dementia patients. We plan to study whether treatment with medication memantine improves BPSD in severe AD patients. Thirty-two AD patients with significant BPSD, including agitation and aggression, will be treated for three months with memantine. Assessments of behavioural symptoms and global clinical outcomes will be completed after one, two and three months of treatment. 