This article reviews the concept of costing, and how cost data have been considered and reported in recent multinational economic evaluations. It appears that current practice frequently does not comply with microeconomic foundations and standards for good practice. A number of studies fail to indicate the year of costing data, the explicit source(s) of such data, the ranges of variables chosen for sensitivity analysis, and the rates used for the translation of currencies and for inflation or deflation. Consequently, caution should be exercised if using such papers as sources of cost data. It is recommended that differences between countries, both in terms of quantities of resources used and of unit prices, should be clearly stated in the presentation of results, as well as the method of calculating overall findings from the various country-specific results.