Cognitive impairment is closely related to real-life functioning in patients with schizophrenia. The aim of the present study was to evaluate the effects of adjunctive treatment with donepezil on cognition in patients with chronic schizophrenia. This was a 12-week, double-blind, randomized, placebo-controlled study of donepezil as an adjunct to antipsychotic drug therapy in patients with chronic stable schizophrenia. Sixty-one subjects were randomized to receive donepezil 5 mg/day (n=31) and/or placebo (n=30). A nine-test neuropsychological assessment battery was administered at baseline and at the end of the study. At the 12-week end point, the donepezil group showed significant improvements in the Wechsler Memory Scale Third Edition Spatial Span, Brief Visuospatial Memory Test total recall and delayed recall, Trail-Making Test Part A, and Category Fluency Test-animal naming (all P <= 0.018). Compared with placebo, donepezil was associated with significant improvement in several cognitive domains, including working memory, speed of information processing, and visual learning and memory (P <= 0.008). The results of the present study suggest that adjunctive use of donepezil is beneficial for improving cognitive function in patients with schizophrenia.