Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO Preparatory Commission)


  • Established: 19 November 1996
  • Duration: Indefinite
  • Number of Signatories: 184
  • Number of Ratifications: 168

The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO Preparatory Commission) is an international organization established at a meeting of States Signatories to the Treaty on 19 November 1996.



Located at the Vienna International Center, Austria, the CTBTO Preparatory Commission prepares for the effective implementation of the Comprehensive Nuclear-Test-Ban Treaty (CTBT)," and for the first session of the Conference of the States Parties to the Treaty. The Preparatory Commission's main tasks are establishing a global verification regime to monitor compliance with the comprehensive ban on explosive nuclear testing and promoting Treaty signature and ratification. The global verification regime consists of the International Monitoring System (IMS) and a consultation and clarification process to clarify and resolve matters concerning possible non-compliance with the basic obligations of the Treaty.

Treaty Overview

The CTBT is a cornerstone of the international regime on the nonproliferation of nuclear weapons and an essential foundation for the pursuit of nuclear disarmament. Its total ban of any nuclear weapon test explosion in any environment will constrain the development and qualitative improvement of nuclear weapons and end the development of advanced new types of these weapons.

The CTBT was adopted by the United Nations General Assembly, and was opened for signature in New York on 24 September 1996. It has achieved strong worldwide support.

Article XIV of the CTBT stipulates that the Treaty will enter into force 180 days after all 44 nuclear-capable countries (those that formally participated in the Treaty negotiations and possess nuclear power reactors and/or nuclear research reactors) have deposited their instruments of ratification with the United Nations. Currently, eight states on that list still must ratify in order for the Treaty to be legally binding. These states are China, the Democratic People's Republic of Korea, Egypt, India, Iran, Israel, Pakistan, and the United States. All but three, Pakistan, India and the Democratic People's Republic of Korea, have already signed the Treaty.


The CTBTO Preparatory Commission has concluded a Host Country Agreement with the Government of Austria and has a Relationship Agreement with the United Nations. The Relationship Agreement with the United Nations provides a framework for cooperation between the two organizations, as the Commission is an independent organization with its own membership and budget. Cooperation between the United Nations and the CTBTO Preparatory Commission facilitates the effective implementation of the Treaty, including the establishment of the global verification regime.

The Relationship Agreement allows the CTBTO Preparatory Commission to participate in United Nations meetings in the same capacity as the International Atomic Energy Agency (IAEA) and the World Trade Organization (WTO). These organizations may propose agenda items for consideration of the other and exchange documents, publications, and other information of mutual interest. The Executive Secretary of the CTBTO Preparatory Commission informs the United Nations of all its activities, such as in his annual address to the General Assembly. Using the United Nations laissez-passer as a valid travel document, officials of the Preparatory Commission engage in global activities aimed at facilitating the entry into force of the CTBT, for example holding regional workshops and conferences.


The CTBTO consists of a plenary body composed of all the States Signatories (also known as the Preparatory Commission), and the Provisional Technical Secretariat (PTS). A State becomes a member of the CTBTO Preparatory Commission upon signing the Treaty. Member States each have one representative in the Commission, who are accompanied by alternates and advisors. Member States support the activities of the CTBTO Preparatory Commission through payment of assessed contributions and participate in the Commission's decision-making process.

Non-signatory States who host or will host IMS facilities are accredited with observer status and may attend meetings and activities of the Working Groups and their subsidiary bodies that are related to the IMS. However, observer status does not permit non-signatory States to participate in the decision-making process of the CTBTO Preparatory Commission.

Preparatory Commission

The main task of the Preparatory Commission is to establish a global verification regime as foreseen in the CTBT so that it will be operational by the time the Treaty enters into force. The verification regime will include procedures for on-site inspections and confidence-building measures.

The Preparatory Commission has three subsidiary bodies: Working Group A advises on administrative, legal, and budgetary matters; Working Group B advises on technical verification issues; and the Advisory Group contributes to financial, budgetary, and associated administrative issues. Both Working Groups make proposals and recommendations for consideration and adoption by the Preparatory Commission at its plenary sessions. Ambassador Aliyar Lebbe Abdul Azeez of Sri Lanka was elected as the Chairperson of Working Group A in October 2013. As of March 2015, Mr. Joachim Schulze of Germany has been acting as the Chairperson of Working Group B. The Advisory Group, with Sir Michael Weston of the United Kingdom as its Chairperson since June 2012, is composed of experts of international standing serving in a personal capacity. Ambassador Abel Adelakun Ayoko of Nigeria is the Chairperson of the Preparatory Commission for 2015.

Provisional Technical Secretariat (PTS)

Under the Executive Secretary of the CTBTO Preparatory Commission, Mr. Wolfgang Hoffmann, the PTS began its work on 17 March 1997. During its plenary session in November 2004, the CTBTO Preparatory Commission elected Ambassador Tiber Tóth of Hungary to succeed Mr. Hoffmann as Executive Secretary. On 1 August 2013, Lassina Zerbo from Burkina Faso became Executive Secretary of the CTBTO. He was elected in October 2012. The PTS has an international staff of approximately 270 members from 70 countries. The PTS cooperates with the host countries in the development and running of an international network of 337 monitoring facilities provided for in the Treaty.

The Secretariat is responsible for overseeing and coordinating the provisional operation of the IMS and the International Data Centre (IDC), which receives, processes, analyzes, and reports on IMS data. The Secretariat is also in the process of developing operational manuals, which guide the various components of the verification regime, including budgetary and work planning.

Point of Contact

Executive Secretary: Ambassador Lassina Zerbo (Burkina Faso)
Preparatory Commission for the CTBTO
Provisional Technical Secretariat
Room E-0750
Vienna International Center
P.O. Box 1200, A-1400 Vienna
Phone: (431) 26030 6200
Fax: (431) 26030 5877


The CTBTO Preparatory Commission prepares for the effective implementation of the CTBT, and for the first session of the Conference of the States Parties to the Treaty.

This material is produced independently for NTI by the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey and does not necessarily reflect the opinions of and has not been independently verified by NTI or its directors, officers, employees, or agents. Copyright 2019.