From January 1980 through December 1982 the Illinois Valley Library System (IVLS) and 33 of its participating libraries conducted an experimental project to test the costs and benefits of OCLC use in small and medium-sized libraries. This report, one of eight describing the results of the OCLC Experimental Project, examines interlibrary loan activities before and after the OCLC interlibrary loan (ILL) subsystem was used in the project libraries. Comparisons are made in terms of time, costs, and staffing levels. The second part of the report examines resource sharing patterns in the IVLS and how they changed during the project. Finally, the attitudes of library staffs toward online ILL are reviewed. Multiple graphs, tables, and figures summarize the data. Appendices include the following: (1) statistical information on project libraries; (2) IVLS Interlibrary Loan Protocols and Summary Card for Terminal Operators; (3) IVLS Request Form and Flow Chart of IVLS Interlibrary Loan Department Procedures; (4) Transaction Study Form; (5) IVLS Interlibrary Loan Department Worklog Study Form and Instructions; (6) Library Interlibrary Loan Worklog Study Forms and Instructions for Terminal Activities and OCLC-Related Work; and (7) Library Log Form for Non-OCLC Interlibrary Loan Activity. (THC)