Recent studies in Alzheimer's disease have focused on behavioral disturbances in the more advanced stages of the illness rather than behavioral and personality changes occurring early in the disease course. We present a new instrument, the Oregon Noncognitive Inventory for Dementia (ONID), that was developed specifically for patients in the early stages of dementia, to identify subtle behavioral alterations that may precede the more severe cognitive changes of Alzheimer's disease. Mildly demented Alzheimer's patients were compared with age-matched healthy subjects on the ONID. Caregivers of these patients reported significantly more of the behaviors addressed by the ONID than did relatives of the healthy elderly. The results indicate that changes in behavior and personality can be reliably reported by family caregivers of patients with mild dementia. Future clinical applications of the ONID might include measuring change in drug trials, longitudinal studies of the progression of change, and differentiating Alzheimer's disease from other dementias based on a characteristics pattern of change.