This paper introduces the Southern African Interlending Scheme (SAIS), describes factors that are prompting a rethink of its nature and structure, and briefly sketches some alternative models for its future. The SAIS, which currently has members in seven countries belonging to the Southern African Development Community, had its origins before the Second World War. By the early 1980s it was functioning as a fully decentralised system served by union catalogues on microfiche. In spite of the political barriers created by the apartheid system, libraries in the relevant countries participated in the SAIS freely, without having to use international interlending procedures. The founding of the South African Bibliographic and Information Network (SABINET) in 1983 made possible the automation of interlending transactions, but it also had unintended consequences for the comprehensiveness of, and access to, union catalogues. The introduction of the cost recovery principle in 1989 had further negative consequences for libraries serving less affluent communities and institutions, particularly those in countries other than South Africa. Ironically, as the political barriers to trans-border transactions fell, they were replaced by economic obstacles. More recent developments that have affected or will affect the SAIS are: the decline of library funding in South Africa; the advent of regional consortia and higher education library consortia; changes to the structure and services of SABINET; the establishment of a new network initiative, SABONA, in competition with SABINET; and a possible shift from print-on-paper to electronic journal subscriptions. These developments are forcing a rethink of the structure of the SAIS, and in view of this a working group of the State Library's Advisory Committee on Document Delivery has been developing a number of possible future document supply models for South and Southern Africa.