A discussion of current economic concepts of regionalism and "second-best" worlds as they relate to problems of United States and Japanese aid programs in less-developed countries. Multicountry associations have been formed for many purposes with varying success. In the economic field, the most reliable criterion for membership appears to be common purpose combined with divergent capabilities rather than geographical proximity. In spite of some differences, both United States and Japanese aid programs confront the same basic problems in understanding and influencing development in the less-developed countries. Experience seems to indicate that people, policies, and politics, not investment, are the controlling factors. This paper was prepared for a conference on Japan-U.S. Relations and Asian Security Problems held April 1-4, 1968. 8 pp.