Early in 1938, Brazil signed a treaty with Bolivia that would open part of the apparently oil-rich Chaco region to Brazilian exploitation. Up to that time, Brazil's growing but still negligible national effort to find oil within her own territory had proved fruitless; the treaty, however, seemed to guarantee it a supply of oil not controlled by the great international petroleum companies, an important proviso during the nationalistic Vargas administration. Yet Brazil failed to pursue the prospect opened by the treaty until the 1950s, and then its attempts to implement it were defeated by internal economic nationalism. This essay deals with Brazil's abortive efforts in the 1950s to frame and implement a policy for developing its oil concessions in Bolivia. The incident is an isolated example of the difficult international relations which prevail in Latin America.