In a post seminar discussion at the University of Illinois one day in 1967, the question turned to the availability of resources for users of American academic libraries. The insatiable needs of the patrons in all college and university libraries were generally acknowledged. The capability of satisfying these wanton appetites was not so fully understood. It was conceded, furthermore, that resources seemed destined to limitation on most campuses during the foreseeable future. In order for a library to make available its collections it was agreed, therefore, that it must require its patrons to share the materials. No library can be a repository of literary property for the exclusive use of one person or one group, it was concluded. These principles have been recognized for decades in American academic librarianship. No seminar of scholars can add much to these historical facts. The successes or failures of the patrons* responses to this type of library service, however, are amazingly enough rarely known. Even if a library patron agrees philosophically that a collection is assembled for the use of all members of the community, there seems to be doubt that he actually practices what he knows is the rationale for the establishment of academic libraries. iv The argument continues that all patrons do not or will not share resources with others for several reasons. The library is obliged, therefore, to establish regulations, punitive rules, and other measures to elicit return of borrowed materials. Libraries have also taken the position that they must further encourage the sharing of materials by providing reminders to stimulate patron responses. Substantial programs of service and great amounts of time, effort, and funds are expended annually toward this end, but with unknown results. A further exploration of the literature and a consideration of expert opinion indicated that little information existed about the results of these attempts to encourage patrons to share materials by returning them promptly. It was at this point that serious consideration of a study began to germinate. Subsequent inquiries and discussions led to the experimental research described in this document. Although the impetus for selecting the topic was rather simple as stated, the implementation and the execution and the analysis and the interpretation were much more complex in this assignment. These elements were included in an investigation that continued with varying degrees of intensity for nearly twenty-four months.