Dementia with Lewy bodies (DLB) is common. Symptomatic treatment can be difficult. We reviewed nine consecutive patients with DLB (mean age 77.5 [range 67 to 84] years; seven men and two women; mean duration of disease 3.7 [range 1.5 to 8.0] years) who had been treated with donepezil. Each initially received 2.5 to 5 mg per day of donepezil, and was stabilized on 5 mg per day. Donepezil was increased to 10 mg per day in five patients. The mean observation period was 12 (range 8 to 24) weeks. Target symptoms included cognition, hallucinations, parkinsonism, and functional abilities. By both cognitive testing and family reports, cognition improved in seven of nine patients, remained the same in one of nine, and fluctuated in one of nine (mean Mini-Mental State Examination change 4.4 +/- 6.3 points). Function was improved or maintained in six of nine patients and fluctuated in two of nine. Hallucinations initially worsened, then fluctuated in one patient, but improvement in frequency, duration, and content was reported in eight of nine cases. In three of nine patients, treatment with donepezil resulted in worsening of parkinsonism, which in each case responded to levodopa/carbidopa. Treatment of DLB patients with donepezil for 12 weeks most commonly improved hallucinations, and sometimes improved cognition and overall function. Treatment with donepezil was sometimes associated with worse parkinsonism.