There are many rating instruments designed to assess symptoms of agitation in patients with dementia. Most scales require that raters assess multiple specific behaviors over several days, limiting the use of such scales to clinical staff who have direct contact with patients but do not have the time to complete a comprehensive assessment following each period of observation. Also, scales that assess behavior over several days must rely on “secondhand” information describing behaviors not directly observed by the rater. The Pittsburgh Agitation Scale (PAS) is an easy-to-use instrument, based on direct observations of the patient, that was developed to monitor the severity of agitation associated with dementia. Interrater reliability and measures of validity have been established with clinical staff on a busy psychogeriatric inpatient unit and with research personnel in a nursing home setting.