Alzheimers disease (AD) is the most common dementia. Its frequency has increased dramatically in the last years due to the extended length of life. It presents cognitive symptoms inherent to the dementias, and a progressive and insidious deterioration. Aside from the cognitive deficits there are psychiatric symptoms related to the neurodegeneration of the different cerebral zones, with alteration of the neurotransmission. The etiologic hypotheses of the Alzheimers Disease are complex; it is considered that the appearance of the disease is a consequence of the interrelation of genetic and neurobiological processes like colinergic hypothesis, amyloid hypothesis, glutamatergic hypothesis, oxidative hypothesis and inflammatory hypothesis. The diagnosis of the Alzheimers Disease is by exclusion due to the fact that there are no accurate diagnostic methods in the life of the patient. However, the criteria of the diagnosis by exclusion should be relative considering the AD is one of the most frequent dementia, and we have now some possible orientators. The Mild Cognitive Impairment (MCI) is an entity definy because of the memory impairment without another deficit, and a normal global function. However, some studies had demostrated the MCI has an evolution to Alzheimers disease 12% per year. The pharmacological treatment in early stages of the disease is useful to improve the cognitive disorders to slow down the advance of the deficits, and to diminish the psychiatric symptoms such as agitation, depression and the psychosis. The colinesterase inhibitors are the most studied for the treatment of the AD: tacrine, rivastigmine, donepezil,and galantamine. Vitamin E, estrogens, antiinfamatory drugs, ginkgo biloba and another strategies has been utilized with different efficacy. The future will show new horizons in relationship with neuronal growth factor, antiamyloid therapies and genetic therapies.