Australia has recently acceded to the Vienna Convention on Treaties, one of the major codifying treaties concluded under United Nations auspices. Mr Brazil who was a member and later Leader of the Australian Delegation to the Conference that drew up the Convention, examines its scope, including its answer to the question—should the Convention cover the topic of treaty-making capacity of parts of federal States? Mr Brazil suggests that the Convention's rules on reference to preparatory materials as interpretative aids should be adopted by Australian courts. Its restatement of the topic of reservations and its reception of the notion of international public order (jus cogens) are evaluated. The themes of good faith and due process are seen to run through the Convention, which though not yet in force, has already gained wide acceptance.