The risk of psychosis among patients with Parkinson's disease (PD) is high, and the management of these patients remains a substantial problem for physicians. Atypical antipsychotics, despite their advantages over conventional antipsychotics, can cause different side effects and deterioration of PD. Several reports have suggested that donepezil can be helpful in the treatment of psychotic conditions in patients with dementia with Lewy bodies and Alzheimer's disease. This report presents the results of preliminary study of six patients (four women, two men; age range, 60-75 years) with PD (range of duration, 3-7 years) and dementia complicated by psychosis. All patients were treated with antiparkinsonian therapy, and donepezil was added to their regular treatment. The severity of the psychotic symptoms was assessed using the Scale for the Assessment of Positive Symptoms, and extrapyramidal symptoms were assessed using the Simpson-Angus Scale. With the addition of donepezil (as much as 10 mg/day) to their constant antiparkinsonian treatment, five patients had clinically significant (more than 53%) improvement on the assessment scale, and one patient had minimal (24%) improvement after 6 weeks of the treatment. None of the patients had side effects or deterioration of parkinsonian symptoms. The results suggest that donepezil may ameliorate psychotic symptoms in patients with PD, but this will need to be tested further in controlled, double-blind trials.