The present longitudinal prospective study compared results from the Geriatric Depression Scale with those from the Hamilton Depression Rating Scale for 30 dementia patients. The criterion measure was presence of depression as indicated by the psychiatric diagnosis. The psychiatrist and physician's assistant made the Hamilton ratings while the psychology staff administered the Geriatric Depression Scale. The two measures were statistically unrelated from Times 1 and 2 (rs = .26 and .41). Eleven (37%) patients were depressed and nine received antidepressant medications. Sensitivity ratings were 82% and 9%, respectively, and specificity ratings were 88% and 92%, respectively. Possible explanations for the success of the Geriatric Depression Scale and lack of success of the Hamilton ratings in detecting depression in this population are discussed.