This book results from an initiative promoted by the International Water Resources Association, the third of a series of 'Water Forums' bringing together a small number of specialists to discuss relevant issues in water resources. Two previous water forums-the Middle East one in Cairo in 1993 and the Asian one in Bangkok in 1995-had also resulted in books (International Waters of the Middle East: From Euphrates-Tigris to the Nile (Oxford University Press, 1994) and Asian International Waters: from Ganges-Brahmaputra to Mekong (Oxford University Press, 1996)). The third Water Forum, held in São Paulo in 1997, was attended by 33 invited specialists, and resulted in a book with ten chapters, written by 15 authors, and a foreword by Professor Asit Biswas. Three major South American river basins are treated. Despite the focus of the water forums being on internationally shared basins, the book also addresses the São Francisco river, which drains 640,000 km 2 exclusively in Brazilian territory. Professor Biswas is well-known in the fields of water resources, impact assessment and environmental management. He has authored or edited dozens of books. Newton Cordeiro was a former official of the Organization of American States. Benedito