In the course of the last fifty-five years the countries of the Western Hemisphere have developed effective instruments and procedures for cooperative action in many fields of common interest. There is, in the first place, the official governmental machinery for hemispheric cooperation—the Inter- American system—which operates through thirty permanent agencies. There are, furthermore, some thirty-nine semi-official and private agencies (Inter-American, Caribbean, Latin American, and South American regional, as well as bipartite) which have been established in response to recommendations of general or special Inter-American conferences, under the auspices of the government of some one American state, or by private initiative. And, finally, there are seventeen official agencies created by joint action of two states to deal with problems of special interest to them. In all, there are now eighty-six international agencies in the Americas, over half of them governmental. An adequate presentation of this very extensive machinery for collaboration would exceed the scope of an article. We shall only attempt here to show the variety of common interests now served by international agencies in the Western Hemisphere. Of necessity, the description of individual agencies must be rather sketchy but detailed information concerning the history, purposes, internal administration, and accomplishments of all agencies here mentioned may be found in a volume which has just been published by the Carnegie Endowment for International Peace.