In 1980, an ad hoc working group on chemical weapons was set up at the Conference of the Committee on Disarmament, and this group received a formal mandate to negotiate the text of a Convention banning chemical weapons.

From 1987 regular meetings were held with representatives of the civil chemical industry to ensure that its interests were taken into account. Beginning in late 1988 national trial inspections were carried out both at industrial and military facilities to test the verification provisions.

The negotiators decided early on that unlike past treaties and conventions, this treaty would include a verification regime designed to ensure the compliance of States Parties with the treaty's provisions.

Negotiations on a chemical weapons ban treaty went on for 12 years, from 1980 to 1992. Near the end of these negotiations in Geneva, the use of chemical weapons by Iraq, against both Iran and its own Kurdish citizens in Halabja, was brought to world attention. The effect of mustard gas and other agents on ordinary people, and the horrific photographs that were published around the world, made all the more urgent the work of the diplomats on a treaty not only banning the use, production, and stockpiling of chemical weapons, but also a treaty that would contain a mechanism for verifying a State's compliance with the treaty's provisions.

The text of such a treaty, unprecedented in scope and in the stringency of its verification regime, was adopted by the Conference on Disarmament (formerly the Conference of the Committee on Disarmament) in Geneva on 3 September 1992: the Convention on the Prohibition of Development, Production, Stockpiling, and Use of Chemical Weapons and on Their Destruction (Chemical Weapons Convention or CWC). The Chemical Weapons Convention opened for signature with a ceremony in Paris, in January 1993, and was deposited with the UN Secretary-General in New York. The CWC was the first disarmament agreement negotiated within a multilateral framework that provides for the elimination of an entire category of weapons of mass destruction under universally applied international control.

In order to prepare for the CWC's entry into force, which would occur 180 days after the deposit of the 65th instrument of ratification, a Preparatory Commission was established with the responsibility to prepare detailed operation procedures and to put into place the necessary infrastructure for the permanent implementing agency provided for in the Convention: the Organisation for the Prohibition of Chemical Weapons (OPCW). Headquarters for this organisation were established in The Hague, The Netherlands. For four years the Preparatory Commission laid the groundwork for implementing the Convention: working toward agreement on unresolved issues, establishing procedures for States Parties to make declarations, and most importantly the training of more than 200 inspectors who, by inspecting both military and industrial sites, would make up the heart of the CWC verification regime.

During this time, in 1995, the Aum Shinrikyo religious cult released the chemical agent sarin in the Tokyo subway and planned other attacks with chemical agents or weapons in Japan. Thousands were injured. This incident proved how dangerous these weapons could be and how real a threat they posed, especially if they were to fall into the hands of terrorist organisations.

The Chemical Weapons Convention entered into force on 29 April 1997, 180 days after deposit of the 65th instrument of ratification, by Hungary. At this time, 87 countries had ratified the CWC and became original States Parties to the Convention. With entry into force, the OPCW was formally established.