Alzheimer’s disease is associated with a loss in presynaptic cholinergic function. It has been suggested that cholinergic inhibitors such as donepezil hydrochloride (Donepezil) could restore this function and improve some of the symptoms of Alzheimer’s disease. Previous work has shown that Donepezil improves cognitive and global function in patients with mild to moderate Alzheimer’s disease. This study reviewed retrospectively 12 patients who had previously had a Tc-99(m)-hexamethylpropylene amine oxime (Tc-99(m)-HM PAO) single photon emission tomography (SPET) regional cerebral blood flow (rCBF) examination and had gone on to receive Donepezil therapy. These patients were recalled for a further Tc-99(m)-HMPAO SPET rCBF examination and the image data sets were compared. The results showed an overall increase in global cerebral blood flow (P = 0.04) averaged over the group with a percentage change in blond flow ranging from -1.8% to 6.4%. However, some patients showed a slight decrease in. blood flow. When the data were analysed in terms of regional cerebral blood flow, we found that the most significant increase in blood flow occurred in the frontal lobes (P = 0.02). ((C) 2000 Lippincott Williams & Wilkins).