Relatively recent developments, ranging from microfilm catalogs to networked circulation systems, have the potential of removing much of the uncertainty from the routing of interlibrary loan requests. The opportunity of purchasing location and availability information changes the performance of a model interlibrary loan network. Data collected in Illinois show that location information is very valuable and filmed catalogs may be worth several hundred dollars per year to the Illinois Interlibrary Loan Network (ILLINET). Illinois experience also indicates that local availability information, obtained from an automated circulation system, has minimal value, but the same information, made available throughout a network, reduces the time to satisfy a request. (Author/PF)