Objective: The pharmacoeconomic guidelines available in the literature or promulgated in many countries are either vague or silent about how drug costs should be established or measured so an international comparison of cost-effectiveness analysis (CEA) results can be made. The objective of this report is to provide guidance and recommendations on how drug costs should be measured for CEAs done from an internationally comparative perspective. Methods: Members of the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) Task Force on Good Research Practices—Use of Drug Costs for Cost Effectiveness Analysis (Drug Cost Task Force [DCTF]) subgroup from several countries were experienced developers or users of CEA models, and worked in academia, industry, and as advisors to governments. They solicited comments on drafts from a core group of 174 external reviewers and more broadly, from the members of the ISPOR at the ISPOR 12th Annual International meeting and via the ISPOR Web site. Results: Drug units should be standardized in terms of volume of active ingredient, regardless of packaging and dosing strength variations across countries. Drug costs should be measured in local currency per unit of active ingredient and should be converted to other currencies using sensitivity analyses of purchasing power parities (PPP) and exchange rates, whichever is more appropriate. When using drug prices from different years, the consumer price index for the local currency should be applied before the PPP and/or exchange rate conversion. Conclusion: CEA researchers conducting international pharmacoeconomic analysis should tailor the appropriate measure of drug costs to the international perspective, to maintain clarity and transparency on drug cost measurement in the context of international drug comparison and report the sensitivity of CEA results to reasonable cost conversions.