This report, which investigates turnaround time for interlibrary loans, presents a 1-month study of the interlibrary loan (ILL) process operating in the Western Slope areas of Colorado during 1980. It comprises introductory material presenting the importance, scope and limitations of the study, problem statement, hypothesis and term definitions; a review of the literature on interlibrary loans; analysis and interpretation of data collected from libraries in the Southwest, Pathfinder and Three Rivers sections of the Colorado Western Slope; and conclusions and recommendations on ILL procedures for the Western Slope. Sixteen figures provide data on the regional library service systems in Colorado and the amount of time needed for various stages in the ILL process. Appendices include samples of the forms and accompanying letter used in the survey and six tables giving figures for the number of libraries participating; the number of filled and unfilled ILL requests from the study period; the longest turnaround time for each step in the ILL procedure; and the median turnaround time for all types of requests studied (an average of 9 days), author/title requests (9 days), periodical requests (12 days), and subject requests (7 days). An 18-item bibliography is attached. (ESR)