We conducted an open-label study designed to assess the effects of tacrine on behavioral changes in patients with Alzheimer's disease (AD). Twenty-eight subjects completed a baseline evaluation and at least one assessment during treatment. Behavioral symptoms and cognitive function were assessed with the Neuropsychiatric Inventory (NPI) and Mini-Mental State Examination (MMSE), respectively. The mean NPI score at the maximum individual dose of tacrine attained was markedly decreased (behavior improved, compared to baseline). Symptoms of anxiety, apathy, hallucinations, aberrant motor behaviors, and disinhibition were most responsive. Subject stratification by dementia severity revealed a substantially reduced mean NPI score only in the group with moderate dementia, independent of cognitive response. Over half of the subjects with cognitive improvement had a marked reduction in behavioral symptoms, particularly apathetic behaviors. These data suggest that tacrine may be beneficial for selected behavioral symptoms in AD patients, particularly at higher doses and in those with moderate cognitive deficits.