The 31 st session of the International Geological Congress was held in Rio de Janeiro, Brazil, August 6- 17, 2000, in consortium with other South American countries, under the sponsorship of the International Union of Geological Sciences, the Brazilian Ministries of Mines and Energy and Science and Technology, through their different agencies and Research Institutes, by the Brazilian Academy of Sciences, the Brazilian Geological Society and other Geo-Societies, in cooperation with many technical and scientific institutions, universities, industrial organizations and government bodies, and support of the Rio de Janeiro State Government and City Council. This large gathering of the IGC family in the 20 th Century was the first IGC session ever held in South America since the first meeting in Paris 1878. More than 4,000 earth scientists and students, 112 exhibitors as well as many accompanying members and guests from 110 countries, met at the Rio de Janeiro Convention Center, located 45 minutes from downtown and Copacabana beach. The daily transit to the Centre offered them the opportunity of seeing some of the most beautiful beaches and scenery in the world. The Scientific Program focused on the Congress main theme: Geology and Sustainable Development: Challenges for the Third Millennium, including 9 Colloquia whose presentations were provided digitally, 4 Special Lectures, 72 Special Symposia, 159 General Symposia, over 2,800 Poster Presentations, 8 Short Courses and Workshops, with the participation of top scientists from over the world. 5750 abstracts were received and all were included and offered to the members present in a CD-ROM. 28 Field Trips were run before, during and after Congress, covering the main Brazilian geological sites and mineral deposits, some extending to Bolivia, Argentina and Chile, with the participation of about 600 people. The main publication, a review book on Tectonic Evolution of South America, with 25 chapters, ca. 70 authors and 800 pages was prepared and launched at the Congress. In addition a special issue of the Revista Brasileira de Geociencias (now Brazilian Journal of Geology) was also distributed, with 134 full papers presented at the Congress.