OBJECTIVES: Studies to produce value sets for preference-based measures of health require a full health upper anchor to be defined if the values are to be used to calculate quality-adjusted life years. In EQ-5D value set studies, this upper anchor could either be ‘full health’ or EQ-5D health state 11111. The objectives of this study were to answer the following questions: What (if anything) makes full health and 11111 different from each other? What important aspects of (full) health are not captured by the five EQ-5D dimensions? METHODS: Data were collected from a broadly representative sample of the UK general public via face-to-face interviews. After completing a computer-assisted valuation questionnaire, respondents completed a pen-and-paper follow-up questionnaire. The follow-up tasks were developed by the study team to elicit additional information about the comparability between full health and 11111 and respondents’ interpretations of those concepts; and to inform the ongoing research agenda around the measurement of health beyond the existing EQ-5D descriptive system. A combination of descriptive and thematic techniques were used to analyse the data.  RESULTS: Data are available for 436 respondents. A sizeable minority (30%) of respondents did not agree when asked whether they considered full health and 11111 to be the same as each other. Many respondents suggested that the five EQ-5D dimensions are not exhaustive of all conditions and health problems. Sensory deprivation (particularly vision and hearing) and mental health were the aspects of health most commonly suggested by respondents as being important but not captured by EQ-5D. CONCLUSIONS: The findings of this study support the choice of areas in which developmental bolt-on work has been conducted to date. Further research is required to establish whether and what people would be willing to trade for improvements in the aspects of health not currently included in the EQ-5D.