ISSUE: Few health systems or reimbursement bodies are explicit about the cost-effectiveness thresholds they use, and even fewer define thresholds based on empirical evidence.   Research is now emerging which seeks to provide empirical evidence for cost-effectiveness thresholds.  Do these provide the correct conceptual foundations for thresholds to guide decisions?  If so, are the empirical estimates helpful for policy?  The sessions will present conceptual and empirical work from the UK (Soares), Argentina (Augustovski) and internationally (Soares).   Basu will discuss the appropriateness of this research in providing appropriate thresholds for decision making in the US and elsewhere. OVERVIEW: To inform resource allocation decisions using cost-effectiveness analysis, decision makers need some idea of the cost-effectiveness threshold.  Such a threshold provides guidance as to the maximum a health system might pay for additional health outcomes.   Two broad concepts of the threshold have emerged.  The first is a demand side one which seeks to base the threshold on public or other preferences about how much funding should be allocated to health care.  This aspirational perspective is the basis, for example, of the WHO-CHOICE threshold recommendations for a given jurisdiction of between 1 and 3 times GDP per capita.  A second concept relates to the supply side, and reflects the health forgone (opportunity cost) when additional resources are allocated to a given intervention rather than to other activities.  This is the focus of recent research undertaken in the UK.  Given the importance of defining cost-effectiveness thresholds alongside cost-effectiveness analysis, research in this area may be considered long overdue.  But what is the correct conceptual and empirical path?