This study aimed to determine the reliability and validity of the Turkish version of Disability Assessment for Dementia (DAD) scale in the Turkish elderly population with Alzheimer disease (AD). The DAD scale was administered to the primary caregivers of 157 patients (age 77.7 +/- 6.8 years) with AD. The Turkish version of the DAD scale showed high internal consistency (Cronbach = .942), excellent test-retest, and interrater reliability (intraclass correlation coefficient [ICC] = 0.996 and ICC = 0.994, respectively). The DAD scale was significantly correlated with activities of daily living (ADL; Modified Older Americans Research Survey ADL) and instrumental activities of daily living (IADL; Lawton and Brody IADL) scales (r = .89, P < .001 and r = .90, P < .001). Disability Assessment for Dementia had a high negative correlation with the Global Deterioration Scale (GDS; r = -.880, P < .001). Post hoc comparisons with Tukey test showed significant differences in the mean DAD scores in different GDS stages. Construct validity was estimated using total score correlation analyses between the standardized Mini-Mental State Examination (MMSE) and the DAD scale. Results revealed high and significant correlation between MMSE score and DAD scale (r = .812, P < .001). The results of multivariate analysis showed that DAD score was not correlated with gender, education, and age. The DAD total score was affected mostly by GDS, MMSE, and duration of the disease. Turkish version of the DAD scale was found to be a reliable and valid instrument to assess functional disability in Turkish elderly patients with AD. This scale assists caregivers and physicians to decide for proper interventions.