The objectives of the study leading to this report were to review, analyze and summarize published library cost data; and to develop a cost model and a methodology for reporting data in a more consistent and useful way. The cost model and reporting procedure were developed and tested on the circulation system of three libraries: a large university library and two large public libraries. The model permits the computation of unit costs for component subsystems of circulation systems. Cost data is summarized and reviewed, and the cost reporting form is included for use by other libraries. A bibliography of 304 references surveyed for cost data is included. (AB)