When Paul Reuter's Introduction au droit des traites was first published in 1972, it instantly became a classic, and was followed by a revised edition in 1985. Shortly before his death, Reuter thoroughly revised and updated the 1985 version for an English edition, taking into account the newly adopted 1986 Vienna Convention on treaties between states and international organizations, as well as recent developments in international codification efforts, undertaken under the auspices of the United Nations International Law Commission, with which he had been very closely associated for many years. This book will be of great interest to students, lawyers, and all those who wish to become more familiar with the legal aspect of treaties, the basic instrument for international relations.