Delirium is commonly encountered in elderly patients in general hospitals. Most patients with delirium respond well within 12 days of commencement of treatment with haloperidol. A significant number of patients, however, does not improve. Three elderly male patients aged 85, 79 and 81 respectively suffering from prolonged delirium and unresponsive to haloperidol or atypical anti-psychotic drugs, responded well within days to treatment with rivastigmine--a cholinesterase-inhibitor. It was very well tolerated. In The Netherlands cholinesterase inhibitors are registered for the symptomatic treatment of Alzheimer's disease. There is some evidence, both from animal and human experiments, that cholinergic deficiency plays a role in certain types of delirium. Therefore treatment of delirium with a cholinesterase-inhibitor seems logical. Controlled studies are needed to evaluate the effects of these types of drugs in patients with prolonged delirium.