Origins
Mercado Comun del Sur (Common Market of the South)
Custom Union: Brazil, Argentina, Paraguay, Uruguay, and Venezuela (pending)
Biggest Trade Block in South America and 4th Worldwide
Treaty signed on March 26th 1991 by Brazil, Argentina, Paraguay and Uruguay
Treaty of Asuncion
Supplemented Brazil and Argentinas already established Treaty of Buenos Aires.
Venezuela signed agreement June 17 2006 (pending)