GPs should consider a diagnosis of dementia when a patient presents with functional impairment in addition to at least two changes in cognitive function e.g. short-term memory, language, reasoning, spatial orientation, or personality change. The patient, friends, family or professional carers should have noticed these changes for at least six months. Patients should be referred to a memory clinic to make a formal diagnosis of probable or possible Alzheimer's disease and to exclude other types of dementia. Key to assessment is a careful history of cognitive and functional changes, medical conditions and past psychiatric history. An objective cognitive assessment is important, and in primary care screening tools such as the General Practitioner Assessment of Cognition provide a useful adjunct to justify referral to specialist services. Patients should have a physical examination and a dementia screen to exclude treatable causes of cognitive impairment. Acetylcholinesterase inhibitors and memantine both slow the progression of cognitive decline and extend independence in activities of daily living. NICE recommends donepezil, rivastigmine or galantamine for mild to moderate Alzheimer's disease, and memantine for severe disease. Primary care is optimally placed to screen for cognitive impairments, to provide essential longitudinal information that will make a diagnosis of dementia safer. Primary care also has a crucial role in primary and, particularly secondary, prevention programmes to tackle excessive weight, lack of activity, smoking, and other lifestyle risk factors for dementia, including Alzheimer's disease, as well as the treatment of medical conditions which increase dementia risk.