A low cost approach to measuring materials availability in small- or medium-sized libraries using an interview questionnaire is described in detail, along with an application of this approach. A rationale for using this method is provided, as well as guidelines for conducting such a survey. Facts of the study are discussed, including objectives, methods of estimating availability, design criteria, staff and materials commitments, the purpose of each of the six questions, when and how to administer the questionnaire, the method of coding and scoring responses, test limitations, and interpretation of results. Sample questionnaires, scoring instructions, and a scoring sheet are provided. A description of a study conducted at the Champaign Public Library and Information Center in March 1979 to evaluate the test instrument and user response to it is appended. This report covers procedures for conducting the interview, sampling of library patrons, and the results of the survey, including responses used, types of materials requested, the success and failure rates of materials by class and item, and the cost of the survey. Eleven tables and a list of 36 references are provided. (RBF)