ISSUE: The calculation of minimally clinically important differences (MCIDs) is common in disease specific outcomes. But how does this concept translate to a cardinal utility scale such as the EQ-5D? Many examples of MCID for EQ-5D now appear in the literature, but do they have meaning? Should we attempt to define MCID for a utility score where the preference weights indicate how much one state is preferred to another? Simon Pickard has worked on a number of MCID studies and will outline the rationale for MCID representing a meaningful difference on a utility scale. Andrew Lloyd is a member of the EuroQol group and will outline discussions that have happened with the EuroQol group on this issue. John Schneider is a health economist and will argue that the role of a cardinal utility measure is to estimate QALYs and cost effectiveness and as such the concept of MCID should not be applied to EQ-5D. OVERVIEW: EQ-5D provides an important input into the calculation of quality adjusted life years (QALYs). To be combined with survival estimates, health-related quality-of-life (HRQoL) measures need to be anchored at zero for dead and one for full health and have cardinal utility scale properties. This requires elicitation using methods of utility score generation such as standard gamble, person or time trade off. Disease-specific HRQoL measures are not subject to the same level of elicitation with the consequence that the resulting scales are not comparable between disease areas. The lack of common scale makes it natural to ask what level of difference on a disease specific scale is clinically meaningful. But what do such estimates really mean for a generic cardinal utility measure? This issues panel represents an important unresolved debate in our field that sits on the intersection between outcomes research and pharmacoeconomics.