OBJECTIVE: There are three main aims of this study. (1) To create a profile of the state of health in the Danish population.For this purpose we selected three multi-attribute classification systems: EQ-5D, SF-36 and 15D. The selection of instruments was based, inter allia, on the availability of validated Danish versions and on the instruments being used internationally. (2) To evaluate the instruments in terms of their validity and reliability in measuring a population’s health status. (3) To compare the instruments in the measurement and evaluation of health-related quality of life. METHODS: The study is based on postal questionnaires, performed by a professional survey institute. A random sample of around 6.000 individuals of the Danish adult population was contacted by phone, asking whether they would be interested in completing the questionnaires. Around 5.000 agreed to participate, and 3.400 responded (a response rate of 68 %). The questionnaires contained all three instruments, including the complete EQ-5D VAS scaling exercise. A randomised experiment with 6 versions of EQ-5D containing varied wording and response categories was also embedded in the study. CONCLUSION: This study will provide a rich data set, the analysis of which should be an important contribution to the measurement and valuation of health-related quality of life both in Denmark and in the wider international context.