The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions in all environments, for military or civilian purposes.


The Treaty was opened for signature in New York on 24 September 1996, when it was signed by 71 States, including five of the eight then nuclear-capable states. The CTBT has now been signed by 180 states and ratified by 145. On 16 January 2007, Moldova ratified the CTBT, completing the ratification of the treaty by all the states of Europe. India and Pakistan, though not nuclear weapons states as defined by the Nuclear Nonproliferation Treaty (NPT), did not sign; neither did the Democratic People's Republic of Korea (North Korea). India and Pakistan conducted back-to-back nuclear tests in 1998, while North Korea withdrew from the NPT in 2003 and tested a nuclear device in 2006. Fifteen other states have not signed. The treaty will enter into force 180 days after the 44 states listed in Annex 2 of the treaty have ratified it. Nine of these have not yet done so, including two nuclear weapon states under the NPT (the United States and the People's Republic of China) as well as all four states outside the NPT (India, Pakistan, Israel and North Korea).


(Article I):

  1. Each State Party undertakes not to carry out any nuclear weapon test explosion or any other nuclear explosion, and to prohibit and prevent any such nuclear explosion at any place under its jurisdiction or control.
  2. Each State Party undertakes, furthermore, to refrain from causing, encouraging, or in any way participating in the carrying out of any nuclear weapon tests explosion or any other nuclear explosion.


Arms control advocates had campaigned for the adoption of a treaty banning all nuclear explosions since the early 1950s, when public concern was aroused as a result of radioactive fall-out from atmospheric nuclear tests and the escalating arms race. Over 50 nuclear explosions were registered between 16 July 1945, when the first nuclear explosive test was conducted by the United States at Alamogordo, New Mexico, and 31 December 1953. Prime Minister Nehru of India voiced the heightened international concern in 1954, when he proposed the elimination of all nuclear test explosions worldwide. However, within the context of the Cold War, skepticism in the capability to verify compliance with a comprehensive nuclear test ban treaty posed a major obstacle to any agreement. On 13 October 1999 the United States Senate rejected ratification of the CTBT.

Partial Test Ban Treaty, 1963

Limited success was achieved with the signing of the Partial Test Ban Treaty in 1963, which banned nuclear tests in the atmosphere, underwater and in space. However, neither France nor China, signed the PTBT.

Nuclear Non-proliferation Treaty, 1968

A major step towards non-proliferation of nuclear weapons came with the signing of the Nuclear Non-proliferation Treaty (NPT) in 1968. Under the NPT, non-nuclear weapon states were prohibited from, inter alia, possessing, manufacturing or acquiring nuclear weapons or other nuclear explosive devices. All signatories, including nuclear weapon states, were committed to the goal of total nuclear disarmament.

Negotiations for the CTBT

Given the political situation prevailing in the subsequent decades, little progress was made in nuclear disarmament until 1991. Parties to the PTBT held an amendment conference that year to discuss a proposal to convert the Treaty into an instrument banning all nuclear-weapon tests; with strong support from the UN General Assembly, negotiations for a comprehensive test-ban treaty began in 1993.

One of the largest issues was the priorities of the different countries. The Non-aligned movement countries were highly concerned with vertical proliferation (more and more bombs, new bomb technology) while the Nuclear Powers were focusing on horizontal proliferation (nuclear bombs being produced by states other than themselves).

Adoption of the CTBT, 1996

Intensive efforts were made over the next three years to draft the Treaty text and its two annexes. However, the Conference on Disarmament, in which negotiations were being held, did not succeed in reaching consensus on the adoption of the text. Australia then sent the text to the United Nations General Assembly in New York, where it was submitted as a draft resolution. On 10 September 1996, the Comprehensive Test-Ban Treaty (CTBT) was adopted by a large majority, exceeding two-thirds of the General Assembly's Membership.

US Ratification of the CTBT

The US has signed the CTBT, but not ratified it. There is ongoing debate whether or not the US should ratify the CTBT. Proponents of ratification claim that it would:

  1. Establish an international norm that would push other nuclear capable countries like North Korea, Pakistan, and India to sign.
  2. Constrain worldwide nuclear proliferation by vastly limiting a country's ability to make nuclear advancements that only testing can ensure.
  3. Not compromise US national security because the Science Based Stockpile Stewardship Program serves as a means for maintaining current US nuclear capabilities without physical detonation.

Monitoring of the CTBT

Geophysical and other technologies are used to monitor for compliance with the Treaty: seismology, hydroacoustics, infrasound, and radionuclide monitoring. The technologies are used to monitor the underground, the waters and the atmosphere for any sign of a nuclear explosion. Once the Treaty enters into force, on site inspection will be provided for where concerns about compliance arise.

The Preparatory Commission for the Comprehensive Test Ban Treaty Organization (CTBTO), an international organization headquartered in Vienna, Austria, was created to build the verification regime, including establishment and provisional operation of the network of monitoring stations, the creation of an international data centre, and development of the On Site Inspection capability.

The monitoring network consists of 337 facilities located all over the globe. As of January 2008, nearly 70 percent of monitoring stations are operational. The monitoring stations register data that is transmitted to the international data centre in Vienna for processing and analysis. The data is sent to states that have signed the Treaty.


Original text derived from Preparatory Commission for the Comprehensive Test Ban Treaty Organization

Signatures and Ratifications

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