This article summarizes the discussion at the joint IFA/OECD Seminar, held during the IFA Congress in Amsterdam in September 2006, on the meaning of "enterprise" in the OECD Model Tax Convention. The article considers the seven case studies examined by the panellists and concludes that there is a worrying lack of agreement on the meaning of such a fundamental concept in the OECD Model as "enterprise" or "business".