Alzheimer's disease (AD) is a neurogenerative disorder that had no effective treatment until a few years ago. Many studies published during the past 20 years showed that the disease is associated with the disruption of brain systems that use acetilcholine. These findings shaped the development of the cholinergic treatment strategies for AD. The cholinesterase inhibitors were the first class of drugs to show positive results in double-blind placebo controlled studies for the treatment of AD. This paper reviews efficacy and safety studies of tacrine, donepezil, rivastigmine, and metrifonate in patients with AD. Factors that may interfere with patients' response to treatment are also discussed, as well as the limitations associated with the use of this class of drugs.