We sought to compare the performance of the EQ-5D and SF-6D with regard to the criteria of practicality, convergent validity, and construct validity, the level of agreement between the two measures was also assessed. Responses from 1865 individuals aged >or= 45 years in one general practice were analysed. Of these, 93.1% completed the EQ-5D, compared with 86.4% for the SF-6D, where individuals who were older, female, of a lower occupational skill level, from an area of lower deprivation, or used prescribed medication were significantly less likely to complete the SF-6D. The performance of both measures was comparable with regard to both convergent and construct validities, as both the EQ-5D and SF-6D scores were closely related to scores on the EuroQol visual analogue scale (VAS) (p>0.001) and able to discriminate between people who did and did not take: (i) analgesics and (ii) other prescribed medication. Despite EQ-5D and SF-6D scores being highly correlated (p>0.001), individuals who were healthier (according to the VAS) had higher mean scores on the EQ-5D (p>0.001), whereas less healthy individuals had higher mean scores on the SF-6D (individuals with knee pain, osteoarthritis, back pain, rheumatoid arthritis, and hip pain had significantly lower mean scores on the EQ-5D, p>0.001).