The United Nations Special COMmission was created by the United Nations Security Council resolution 687 of 3 April 1991, which established the terms a cease-fire between Iraq and Kuwait.
Section C of this resolution called for the elimination, under international supervision, of Iraq's weapons of mass destruction and ballistic missiles with a range greater than 150 kilometres, and UNSCOM was set up to implement the non-nuclear provisions of the resolution while assisting the IAEA in the nuclear areas.
UNSCOM has been responsible for uncovering information on Iraq's weapons programs including biological warfare (the Al-Hakam production facility), the chemical nerve agent VX and other advanced chemical weapons, and Iraq's production of missile engines. The commision has also overseen the destruction of large numbers of ballistic missiles, chemical warheads, launch pads, and the infamous Iraqi "super gun."
Member countries are: Australia, Austria, Belgium, Canada, China, the Czech Republic, Finland, France, Germany, Indonesia, Italy, Japan, the Netherlands, Nigeria, Norway, Poland, the Russian Federation, the United Kingdom, the United States and Venezuela.
Source: http://www.un.org/Depts/unscom