The term "state of source" is used often and as a matter of course in talking about tax treaties and seems to be indispensable for rulings and discussions on double taxation. Thus, it is surprising that the OECD Model Tax Convention on Income and on Capital does not know the term. Its distributive rules designate one contracting state by mentioning a connecting factor - e.g. the situs of immovable property or the residence of the owner of an enterprise - and call the treaty partner state simply "the other Contracting State". The Commentaries and the OECD reports on double taxation, however, use the term abundantly as opposed to "state of residence". This article shows that this terminology is based on an insufficient understanding of the system of distributive rules. The "state of residence" and the "state of source" are not opposites; as long as only two states (and not more) are involved, and therefore only one treaty is applicable, the term "state of source" is redundant. The term "state of source" may, however, be helpful in discussing triangular (polyangular) cases.