SummaryMERCOSUR ‐ Mercado Comun del Sur or Southern Cone Common Market ‐ is a customs union formed by Argentina, Brazil, Paraguay and Uruguay. It covers a population of 180 million and a geographical area of 17 million km2. In terms of economic influence, it ranks fourth after the European Union (EU), NAFTA and Japan. Its goals ‐ which must be attained with the preservation of the environment in mind ‐are: the free circulation of goods, services and other productive factors; the establishment of a common external tariff; the adoption of a common commercial policy towards other states; the co‐ordination of macro‐economic and sectoral policies; and, the harmonization of national legislation.The environmental policy of MERCOSUR – outlined recently in‘Basic Guidelines of Environmental Policy’– deals with the following needs: inclusion of environmental costs in cost analysis; adoption of adequate practices and sustainable management of natural resources; control of potential adverse activities; adoption of minimization and treatment practices; cleaner technologies and recycling; monitoring of shared ecosystems; co‐ordination of international acts; and, institutional strengthening and environmental management of tourism. Further, the recent Interregional Agreement between MERCOSUR and the EU (preparatory to an Interregional Association) has set, on its yet early agenda, the need to commit to environmental protection for a broader and