This article reports on the proceedings of the conference on the legal status of the Commentaries on the OECD Model Tax Convention on Income and on Capital, held in September 2006 and hosted by Leiden University, the Netherlands. The debate on the legal status of the OECD Commentaries recently received new impetus following the publication of a study on Arts. 31, 32 and 33 of the Vienna Convention on the Law of Treaties and their application to tax treaties. The primary focus now is on the general principles of international law. In particular, opinions differ on the question whether the Commentaries can be a source of legal obligations through the principles of acquiescence and estoppel, both of which are founded on considerations of good faith and equity and provide specific protection of settled expectations. This article summarizes the presentations of the conference speakers and the subsequent panel discussions.