This paper examines rationales, aspirations, assumptions and methods shaping an international assessment of learning outcomes: the OECD's Assessment of Higher Education Learning Outcomes (AHELO) feasibility study. The first part of the paper is analytical, exploring formative rationales, and shaping contexts and normative perspectives that frame the evaluation. The discussion then turns to review scientific and practical challenges involved in an assessment of the study, which will be tested on an international scale, and to sketch ideas and innovations being created in response. In conclusion, the paper offers reflective suggestions for positioning AHELO in global higher education, should the initiative prove feasible.