The cholinesterase inhibitors (tacrine, donepezil, galantamine and rivastigmine) were the first drugs licensed for mild to moderate Alzheimer's disease (AD). Recently, the use of donepezil has been extended to severe AD. Tacrine was the first to be marketed, which, although beneficial in AD, shows a high incidence of adverse effects and is rarely used. It will not be discussed further. The cholinesterase inhibitors are widely prescribed and continue to be the first line in the treatment of AD. Considering the mode of action of the cholinesterase inhibitors it is not expected that they will alter the course of the disease, but they may help with some of the manifestations of dementia.