The etiology of Alzheimer's disease (AD) is still unknown, and a definitive diagnosis of the disease can be determined only at autopsy or by brain biopsy. AD can be characterized by various structural changes, including cerebral cortical atrophy, neuronal loss, neuritic plaques, and neurofibrillary tangles. The primary defect involves reduced activity of choline acetyltransferase. Neurotransmitters, such as norepinephrine, serotonin, dopamine, and somatostatin, are also compromised. Treatment of AD requires maintenance of a consistent lifestyle and environment for the patient, as well as counseling and support for the patient's family. Medications, which have been effective in some patients, are primarily used to improve cognitive function and modify behavior. Cognitive medications such as tacrine hydrochloride and physostigmine have proven beneficial in some patients, while behavioral medications have been effective in the treatment of depression, aggression, agitation, and anxiety associated with AD. However, the side effect profile of each medication and its probable overall benefit to the individual patient should be evaluated before beginning therapy. Continued research in patients with AD is required to identify medications that will consistently ameliorate the memory loss associated with the disease.