In Professor Rosenstein-Rodan's seminal article on international aid,' one aspect is not fully developed. The capacity to absorb aid during I96I-76 by underdeveloped countries is calculated with full reference to expected rates of growth, but the capacity to pay of developed countries pays no attention to their growth. A capacity to pay criterion is evidently in use, since Rosenstein-Rodan bases the distribution of contributions on a progressive principle. Furthermore, growth rate projections are likely to be just as sound (or unsound) for the developed as the underdeveloped nations, especially now that the Twentieth Century Fund estimates are available.2