Alzheimer's disease (AD) is the most common etiology of dementia. Its incidence increases with age following an exponential trend of line between 60 and 90 years old. Anti-cholinesterasic drugs reduce modestly AD symptoms. However, they have no basic impact on the pathological evolution of the disease. Memantine offers another therapeutic approach in AD with a dissimilar mechanism of action, confronting neurotoxic effects of glutamate overload. It prevents the elevation of glutamate which destroys cholinergic neurons by inhibiting the N-methyl-D-aspartate (NMDA) receptors. Its clinical efficiency has been demonstrated during 28 weeks with 20 mg/day, in patients presenting moderate or severe AD and mild or moderately vascular dementia. Its use in association with anti-cholinesterasic (donepezil) revealed more interesting results with a significant improvement of cognitive functions and activities of daily live, compared to association placebo-donepezil. We are waiting for results of further lenghter studies, including more, well-defined, patients.