As part of the effort of the NIA Alzheimer's disease cooperative study to develop improved instruments for quantifying effects in Alzheimer's disease (AD) clinical trials, patterns of agitated behaviors were evaluated with the Cohen-Mansfield Agitation Inventory (CMAI) in 241 AD patients and 64 healthy elderly controls with valid baseline assessment on the CMAI. The test-retest reliability of the CMAI over 1 month was good (r = 0.74 to 0.92). Physically and verbally nonaggressive behaviors were most often reported, whereas physically aggressive behaviors were rare. Frequency of agitated behaviors increased with dementia severity, especially for patients with a Mini-Mental Status Exam score of 0-4. Agitation tended to increase in the evening with dementia severity for the more impaired patients. Amount of agitation did increase after 12 months in all but controls and mildly demented patients. The CMAI shows promise for evaluating a unique aspect of behavior and may be useful in assessing the effects of cognitive enhancers and other types of psychotropic drugs on behavior in dementia patients.