Alzheimer’s disease is the most frequent cause of dementia. It usually evolves in three stages; hippocampic (mnesic disorder), occipito-temporo-parietal (speech disorder, apraxia and Gerstmann Syndrome) and global (extrapiramidal symptoms). Other forms of presentation are mixed dementia (AD and cerebrovascular disease) and mild cognitive disorder (does not meet all diagnostic criteria for AD). This article reviews epidemiological data and diagnostic criteria and comments on difficulties for differential diagnosis. Treatment is briefly reviewed, emphazising the importance of psychosocial care and the need for further research