Behavioral and Psychological Symptoms in Dementia (BPSD) are, beside cognitive disorders, major features of Alzheimer's disease and related disorders. Diagnosis is important to enhance our knowledge of the pathophysiology of dementia and of their functional consequences for patients and caregivers. Pharmacological and non-pharmacological management of dementia depends to a large extent on the presence of BPSD. A committee of geriatricians, neurologists and psychiatrists specialized in dementia (THEMA 2) has promoted an epidemiological, diagnostic and therapeutic update in this field. This work was based on the BPSD Consensus Conference Report edited in 2000 by the International Psychogeriatric Association. This report was updated with the most recent literature reports, and was adapted to the French environment. This paper is a synthesis of this meeting, validated and corrected by the entire Thema 2 group.