OBJECTIVE Katz Index of Independence in Activities of Daily Living Scale (Katz ADL) is a widely used tool to assess the level of independency in older adults. The objective of this study was to assess the validity and reliability of the Turkish version of the six item Katz ADL in geriatric patients aged 65 years and older. METHODS The participants were recruited in a geriatric medicine outpatient clinic (n=211). The Katz ADL was translated to Turkish and it was administered with the Barthel index (BI) and SF-36 physical functioning subscale (SF-36 PF) which are already validated in Turkish. Reliability was assessed by internal consistency, interrater and test-retest analysis. Construct validity was assessed by Spearman correlations between the Katz ADL and other functional status indices. RESULTS The internal consistency was high (Cronbach's α=0.838). The test-retest reliability and inter-rater reliability were excellent (ICC 0.999 [0.999-1.000 95% CI]). Regarding the convergent validity strong associations between Katz ADL, BI and SF-36 PF were demonstrated (rs=0.988, p<0.001 and rs=0.674, p<0.001). CONCLUSIONS Validating an instrument, which has originally been developed in a different culture, is a complex but neccessary task. It provides an opportunity for comparison of information across different cultures. To our knowledge, this is the only study to demonstrate reliability and validity of the Katz ADL-six item version in the geriatric population living in Turkey. Turkish version of the Katz ADL is a valid and reliable scale to detect the disability status in the basic activities of daily living in older adults.