By examining the different methods and processes by which national data gathering agencies compile and submit their findings to the Organization for Economic Cooperation and Development (OECD), the authors (1) assess the methodological challenges of accurately reporting tertiary completion and graduation rates cross-nationally; (2) to examine the incongruence of existing internationally comparative data on tertiary completion, particularly within the OECD; and (3) to offer policy recommendations for increasing the congruence and comparability of U.S. higher education data with that of other OECD countries (and the rest of the world). (Contains 5 tables, 3 figures, and 4 footnotes.)