Delirium is now the preferred term to describe acute confusional states. It is experienced by 10 to 30% of all hospital inpatients. Delirium is potentially reversible and is related to several adverse outcomes, including increased hospital length of stay, poor functional status, persistent cognitive impairment, need for institutional care and probably mortality. Disruption of the cholinergic system has been proposed as a key mechanism of delirium. Cholinesterase inhibitors enhance the cholinergic system and there have been reports that they might be beneficial in treating delirium.