The concept of memory centers is based on a multidisciplinary approach to memory disorders and dementia, especially Alzheimer's disease, a public health challenge. The first memory centers were established in the 80s in the US and the British Isles. The aims of these centers are to make a diagnosis (and to reassure the 'worried well'), to detect dementia, to provide a service for their management, to educate care takers, to evaluate new therapies, and to contribute to clinical and basic research. Follow-up is crucial. The first memory centers all experienced long delay to diagnosis of dementia and found that Alzheimer's disease was the first cause of consultation. These observations led to the creation of such centers in many countries. A survey of 20 French memory centers defined the "ideal memory center": an identified structure with a clinic and a day-care unit for diagnosis and follow-up, with neurological, psychological, psychiatric, and geriatric skills. It must be part of a medical and social network for the management of dementia and participate in a network of memory centers at the regional and national level. Relationships between dementia and somatic diseases, frequent in demented patients, are still poorly known. Dementia interferes with the clinical expression, the management, and the prognosis of somatic diseases, some of which, such as cardiovascular conditions, are possibly linked with dementia. Conversely, somatic diseases may rapidly worsen the cognitive state and induce delirium, leading to hospitalization. Medical wards are not ail appropriate. Memory centers must also be involved in these care, educational and research issues.