Introduction: Alzheimer's disease (AD) is described by structural and functional disturbances of the human brain. The amyloid fibril proteins are located and deposited inside neurons as neurofibrillary tangles. These are also deposited extracellular compartment as amyloid plaques. These changes are accompanied by the progressive disorder and loss of nerve cells that are accountable for the loading and managing of information. Finally, AD patients are suffering from loss of memory and cognitive abilities with intense behavior changes. The world's population is getting older; an estimated 35 million have dementia worldwide and it is predicted to increase to 65 million by 2030. Conclusion: Nowadays, the certain diagnosis of AD in the early stages is difficult. Although definite early diagnosis can be obtained by biopsy, probable diagnosis through clinical symptoms is crucial. Unexpected numbers of people are at the risk of AD. This issue needs more effort to finding the effective preventive-therapeutic measures. Improving our knowledge on the exact mechanism of AD is important in designing of these approaches.