The Pacific Southwest Regional Medical Library Service (PSRMLS) studied how health professionals use documents obtained through the regional medical library (RML) network and how various factors, such as delivery time, affected that use. A random sample of libraries in Region 7 of the RML network was selected to survey health professionals who had received documents through the interlibrary loan (ILL) network. The survey provided data about the purposes for which health professionals requested documents, how the immediacy of need for the items affected their usefulness, what effect the obtained information had on the health professionals' work, and whether the illustrations represented an important part of the information content of the items. Survey results provided a positive assessment of the ILL network. Results also verified the basic value of the materials provided to health professionals through ILL and identified some areas for consideration in future network development. Users of the documents indicated that the network works efficiently and effectively to provide timely and useful information needed by health professionals. Technological developments in electronic information transmission and imaging will further enhance network operation in the future.