This e-book deals with National Libraries and their role in document supply. Traditionally document supply within countries is either the responsibility of the National Library or of the national professional body for librarians. The development of OPACs and in particular OCLC's WorldCat has meant that librarians often go direct to a holding library. This is especially so when document supply is international, whether for books or for articles, for returnables or non returnables. However National Libraries still have a role to play as is evidenced by the articles in this issue.