This pilot study evaluated response of negative symptoms (NS) to methylphenidate in patients with dementia and relationships between NS, depression, and cognitive deficits in these patients. Consecutively admitted patients with NS and dementia--12 with dementia of Alzheimer's type and 15 with vascular dementia--were rated on severity of NS (SANS and PANSS-N scales), depressive symptoms (Ham-D), and cognitive impairment (MMSE) before and after treatment with methylphenidate. NS decreased significantly, and cognitive scores increased. A decrease in depression scores was nonsignificant after all variance attributable to NS was removed. NS, depression, and cognitive scores were not significantly intercorrelated. Results were similar for Alzheimer's and vascular dementia patients. Negative symptoms in dementia patients appear responsive to methylphenidate treatment. This effect may underlie putative changes in symptoms of depression observed by other researchers.