States the law relating to treaties from an international aspect and in the light of international sources, while at the same time preserving the point of view of the average common lawyer. Lord McNair was strongly of the opinion that the common law of the British Commonwealth and the United States can and must in the future make greater contributions both to the content and to the practical application of international law. This classic work, first published in 1961 and now available again, retains its usefulness for practising international lawyers and academics concerned with all aspects of the making, application, enforcement, breach, or alteration of treaties.