The psychometric properties of the clinician, informant, and self-rated versions of the Apathy Evaluation Scale (AES-C/I/S) were examined using data on 121 outpatients seen in a behavioral neurology clinic for the assessment of dementia and associated neuropsychiatric disorders. Two factors, apathy and interest, were identified for the AES-C and the AES-I. The AES-S had only an apathy factor. The AES-C was found to have fairly good psychometric properties. However, from a diagnostic point of view, the AES-I provided the greatest sensitivity and the strongest positive and negative predictive values. Generally, the AES-S performed poorly compared with the AES-C and AES-I.