The submission by the Government of the United States to the Government of Canada on May 28, 1938, of a rewritten draft of a Great Lakes-St. Lawrence waterway treaty brings to the forefront again the desirability of concluding a comprehensive agreement between the two Governments for a mutually advantageous utilization of the available navigation and power resources along the boundary basin. In view of the heightened interest in both the United States and Canada, a reexamination of the diplomatic correspondence between the United States and Great Britain and Canada since the end of the nineteenth century regarding the diversion of waters in the United States or in Canada which affected interests in the other country is opportune. It is of significance to note the positions taken by the United States and Great Britain and, later, Canada, in diplomatic negotiations and by significant municipal acts, as to the legal rights of the United States and Canada to the use or diversion of (1) boundary waters, (2) waters which are tributary (and entirely within the territory of one country) to boundary waters, and (3) waters of rivers flowing across the boundary. The distinction between the first situation and the second and third is an important one to observe.