OBJECTIVES: An accepted practice with unresolved issues in economic evaluation is the discounting of future costs and benefits. Many people conducting evaluations view discounting as a technical matter and look to guidelines for the proper rate. Therefore, we ask three questions about international guidelines: 1) what discount rate(s) are recommended; 2) do they differ for costs and health outcomes; 3) what is the underlying theory for discounting and rationale for the rate(s)? METHODS: We review recommendations about discounting in international guidelines according to underlying theory used to recommend discounting, suggested rates, rationale for particular rates, whether a different rate was suggested for health outcomes, and what literature was cited. RESULTS/CONCLUSION: Australia, Canada, and Ontario recommend discounting costs and health outcomes at 5%, the US 3%, New Zealand 10%, and the Netherlands 4%, while the UK recommends 6% for costs and 1.5% for health outcomes. Most countries recognize the controversy, yet remain unconvinced that health outcomes should be discounted at different rates. While the primary stated underlying theory for discounting is time preference, the rationale (if provided) for the particular rates recommended varies across countries. Most often, it relies on empirical estimates of government bond rates and/or notions of international consistency reflecting potentially conflicting principles. Implicit appeals to measure pure time preference also exist; however, this may not be measurable if time and health are inextricably linked. Furthermore, some health outcome measures may already include individuals’ time preferences potentially leading to double discounting. Implications will be discussed.