The law of international organizations, including the institutional law, has been somewhat neglected in the past, even though, or perhaps because, international organizations are creations largely of the 20th century. In my treatise on Principles of the Institutional Law of International Organizations, first published in late 1996 and going now, at the request of the publisher, into a second edition, I directed attention, perhaps in a seminal way, to this institutional law, its importance and its qualification to be considered a specific category not only of general international law but also of international organizational law. In my view there is ample room for further thorough study of various aspects particularly of this law without neglecting the functional international law of international organizations. Apart from principle, their application or non-application in practice may usefully be studied. This by itself justifies a law journal devoted to the subject of international organizational law in general. Moreover, the justification is further reinforced by the fact that now international organizations have become a feature of everyday life in the world. Here, at the risk of repeating what I have said in my book referred to above, because such repetition can only emphasize the importance of the subject matter, I shall concentrate on four aspects which are relevant to international organizational law, to its importance as a part of international law and to its influence on international relations: (i) the pervasiveness of international organizations; (ii) the concept of international institutional law; (iii) its nature; and (iv) its sources.