Though often portrayed as one of the most promising regions in Brazil, and despite the fact that it has been taken over for the last thirty years by various development projects, the São Francisco valley remains one of the most underdeveloped areas of the country. The history of its occupation partly accounts for this situation : the São Francisco is the river of the sertão. The various attempts at reclaiming the region, which began in 1946, are due to various motives, some of them political, but they are also due to a mythical view of the São Francisco as being the "river of national unity ". From 1948 to 1967 the CVSF was rather unsuccessful, probably because it was given too many tasks to carry out at once. Since 1967 the Suvale and then the Codevasf have focussed their action on a few areas in which their main activity is the irrigation of agriculture, the development of which is threatened by the needs of hydroelectric-power. The competition for water therefore makes it necesary to reappraise the future of the valley, which is graduaily being integrated into the economy of Brazil's coastal regions.