The use of information regarding the ages of library items is a standard component of many approaches to weeding library collections, and has a long history in the literature of collection management. Current and past approaches to using aging information to make weeding decisions make use of very arbitrary decision criteria. This study examined the actual aging patterns of public library materials as a precursor to the production of a set of collection management procedures based on sophisticated analyses of aging data. The operational objectives of the study were (1) to develop a set of profiles of the aging characteristics of public library collections, based on analysis of a body of diverse public library holdings data; (2) to formulate a set of collection management guidelines based on the aging profiles, with detailed descriptions of appropriate analyses and their interpretation; and (3) to design an easy to use, flexible computer program to aid in the application of the guidelines. This report covers the problem statement and objectives of the study; the background and context of the study; approaches to weeding library collections; methodology; sample; data collected; data analysis; sample application of age data to collection analysis (Profile 1--the 90% retention rate and Profile 2--curve examination); comparison of the percentage and curve examination methods; continuation of the project; and dissemination of project results. Thirteen notes/references are included, and 109 figures are appended. (BBM)