The OCLC Interlibrary Loan (ILL) Subsystem was designed to facilitate resource sharing among OCLC participating libraries, thereby enabling libraries to expand the range of library resources available to patrons. The final report describes subsystem design and functional uses of the ILL subsystem. A functional overview explains the file, searching, record creation, and ILL response. Descriptions of design and methodology in developing the subsystem, results of testing the subsystem, and prospective field testing are presented. A bibliography, list of system error messages, and reprint of an article on the subsystem are appended. (Author/KP)