The EuroQoL-5D (EQ-5D) is a brief, multi-attribute, preference-based health status measurement. The objective of this study was to assess the validity and reliability of EQ-5D in older adults with and without dementia in Mexico City. The Study on Aging and Dementia in Mexico (SADEM) was a survey of 3101, Mexican adults (60 + years old). An in-home face-to-face interview was administered. EQ-5D using ranking to rate states on a 100-point visual analogue scale; Daily Living Activities (ADL), Instrumental Activities of Daily Living (IADL), Mini Mental State Examination (MMSE), Short Form of the quality of life survey (SF-36), and Charlson comorbility index were used for comparison. The validity and reliability of EQ-5D were tested. We identified states of health for direct valuation; state 11111 ("no problems") had to be included because it was essential to the reseating (onto a 0-1 scale) of the visual analogue scale data. We included all plausible combinations of levels across each of the five EQ-5D dimensions and evaluated any significant interaction effects and factorial designs, based on balanced complete blocks. The EQ-5D was applied to 3101 older people, of whom 109 (3.4%) had dementia. The general reliability of EQ-5D for cases was 0.80 and for controls 0.76, for each dimension. We had a total of 103 combinations for controls and 45 for cases. The percentage for the state of health "no problems" (11111) for controls was 30.4%, and had the highest percentage of cases (8.8%). The resulting valuations form the basis for clinical use and facilitate the interpretation and evaluation of health care. Copyright © 2013 John Wiley & Sons, Ltd.