Development of agents that provide effective treatment of dementia of the Alzheimer type (DAT) has been extraordinarily difficult. A useful addition to a clinician's portfolio of practical therapeutic agents would have a number of characteristics, including ability to enhance cognitive function, acceptable tolerability, and ease of administration. One currently available drug for the treatment of DAT that has these characteristics is donepezil. The objective of this report is to review results of treating patients with mild to moderate DAT with the recently available reversible acetylcholinesterase inhibitor, donepezil hydrochloride. A review of case reports from six patients, some of whom received up to 2 years' treatment with donepezil 5 or 10 mg/d in open-label trials is presented. Clinical observations included physician and family impressions as well as Mini- Mental State Examination scores. In the patients reviewed, donepezil administration effected a modest but clinically important symptomatic cognitive improvement; no change or a less-than-expected cognitive decline when compared with the projected decline in cognitive scores for untreated patients; or decline indicative of lack of response to treatment. The tolerability of donepezil in this small patient sample was consistent with findings from large-scale controlled clinical trials. Treatment with donepezil may enhance cognition in many patients with mild to moderate DAT. Because improvement of cognitive function is an important treatment goal for caregivers and clinicians alike, donepezil represents a clinical option for the treatment of DAT.