Data sources were derived from and methodologies included observation of shoppers, stagings of shoplifting incidents, self-reports of shoplifting by students, and self-reports of employee theft by retail employees. Other methods included shopper interviews, a review of existing retail records, offender process tracing, and evaluation of shoplifting courts through interviews. Field feasibility tests were performed for each method to determine its practicality and usefulness for future research. An intensive site-specific approach was used; it involved conducting feasibility tests at only one or two sites so that the development and refinement of measures and measurement procedures could occur under relatively uniform conditions and allow for monitoring and immediate feedback. The procedures for observing shoppers and staging shoplifting were given special attention because of their potential for determining a store's actual shoplifting rate, as well as the actual characteristics and behavior patterns of shoplifters. Based on over 200 observations in a major department store, it was estimated that about 7.8 percent of customers entering the store shoplifted during their visit. Results also indicated that all the proposed measurement strategies are generally feasible for future research, given some modifications. Techniques were feasible in terms of minimal implementation problems, relative cost, and the degree of validity. Detailed descriptions of each method and feasibility tests used, tables, footnotes, and eight appendixes presenting descriptions of the study's staff training, other aspects of study methodology, and data collection instruments are included. A list of 21 references is given. For related reports, see NCJ 73535-36. (Author abstract modified)