Apathy and loss of insight as correlates of behavior in Alzheimer's disease (AD) were studied in 40 patients by using clinical scales and cerebral blood flow measurements from SPECT imaging. Apathy was significantly correlated with decreased right temporoparietal perfusion and problem behaviors. Loss of insight was significantly correlated with decreased right temporo-occipital perfusion and impairment in daily functioning. Dementia severity as measured by the Mini-Mental State Examination (MMSE) was a poor predictor of behavioral problems or daily functioning. These data suggest that global measures of cognitive ability, which are weighted toward measuring left hemisphere function, are less important as indicators of management problems in AD than are measures of right hemisphere function such as motivation and insight.