This analysis of the demand for public library services in Franklin County, present and future, as the basis for the study's recommendations for future development of the public library system of the County, takes out in some directions new to library planning practice. The study makes a marketing and systems approach to the problem of measuring and projecting the demand for library services, and of developing recommendations as to facilities and capital costs required, and thus permits application of some new methods and measures. Among the innovative features are the development of the measure, "user-visits" to quantify library usage on a uniform basis for each library and branch; and the measure, "index of space utilization," to evaluate the intensity of usage relative to public space available in each library; and the classification of library visitors by census tracts of their home residences to define the "Primary Service Area" of each library and branch. It is hoped that the methodology here developed, with ensuing refinements, will contribute significantly to library planning in the future. (Author)