The "Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and under Water", of 1963 (signed by original parties on 5th of August 1963, opened for signature on 8th of August 1968, entered into force on 10th of March, 1963), more commonly known as the Partial Test Ban Treaty (PTBT) is the precursor to the much later Comprehensive Test Ban Treaty (CTBT). The PTBT essentially seeks to limit the testing of nuclear weapons to being underground, so as to limit the environmental effects of such testing. Unlike the CTBT it does not seek to completely do away with nuclear weapons testing and development. It was, however, an important first step along the way towards an end to the armaments race, and towards complete internationally supervised disarmament, the goals of which are mentioned in the preamble to the PTBT. The preamble also mentions the desire to conclude an agreement for the complete ban of nuclear testing.

The PTBT is an extremely short treaty, but it is as meaningful as it is brief. The bulk of the treaty is contained in one important article.

In article one, each party to the treaty agrees not to test, or to cause, participate in, or encourage, the testing of nuclear weapons in the atmosphere, in outer space, or in its territorial waters or the high seas. Article one also reaffirms the desirability, as agreed to in the preamble, of the conclusion of a treaty to ban underground testing also.

The remaining articles of the PTBT relate to organisational matters, such as the treaty's amendment, entry into force, and validity etc.

Important to note is article four's mention of the treaty's unlimited duration. The partial test ban treaty was not intended to be a temporary solution to the problem of nuclear weapons, rather, it was an important first step. The PTBT went into creating the international political momentum out of which the Nuclear Non-Proliferation Treaty arose. Many years later, the Comprehensive Test Ban Treaty (CTBT), which went one step further than the PTBT and banned underground testing of nuclear weapons, was drafted. Even though, to date, the CTBT has not entered into force, the mere fact that it has been written, and supported by a great number of the world's countries, owes its truth to the adoption in 1963 of the Partial Test Ban Treaty.

Full test of the Partial Test Ban Treaty is available via UN Disarmament - Status and Text of Treaties.