This article describes the present legal regime applicable to the Rio de la Plata, the wide river shared by Argentina and Uruguay. The Plata, which drains an extensive basin covering much of Argentina, Uruguay, Paraguay, Bolivia and southern Brazil, is an important gateway for trade with the interior of the South American continent. The article discusses some of the issues surrounding the exact nature of this body of water and the consequences and present status of the question under international law. The article traces some of the geo-political interests which have historically shaped the diplomatic and legal practices of the riparian states, Argentina and Uruguay, up to the signing of the 1973 Treaty creating a special regime for the Rio de la Plata. This comprehensive agreement, the Treaty of the Rio de la Plata and its corresponding Maritime Boundary, lays the framework for regulating most human activities taking place in the river, in addition to resolving the thorny questions arising from the exercise of each State's respective jurisdiction. The respective powers of the riparians are analyzed for each of the different areas and zones into which the river is apportioned, as well as the attributions which may be exercised by either State in the zones of exclusive jurisdiction and in the so called common zone. Issues such as pollution prevention, pilotage, scientific research, fishing, navigation, works and rescue operations are comprehensively described. The article concludes by portraying recent developments concerning the upgrading and modernization of the Plata's infrastructure for navigational purposes in the context of the regional trend toward privatization and deregulation.