As part of a Universal Availability of Publications (UAP) program, this report describes the current situation in international interlending and possible future models. From a review of literature and statistics previously collected, and a 1979 study of 15 international supply centers, it is concluded that international loan demand is increasing rapidly and that satisfaction rates and speed of response vary greatly. Secondly, two further studies are described which evaluate the extent to which distance affects speed of supply in international loans. It is reported that in 1979/80 no significant difference was found between supply time from India to five other Asian countries, and supply time from the British Library Lending Division to the same Asian countries. Based on data collected in the above studies, a discussion of factors relevant to the planning of international availability is presented. The components and requirements of an international supply system, photocopying of materials, cost recovery, barriers to international availability, and the effect of technological development on international lending are among the factors considered. Finally, several possible patterns of international availability are identified and evaluated, including worldwide, regional, national, and cooperative interlending models. A major distinction is made between copiable and non-copiable materials in these models of international availability. (ESR)