Two Association of Research Libraries member libraries, the University of Illinois at Urbana-Champaign (UIUC) and Pennsylvania State University (Penn State), evaluated their monograph acquisition approval plan profiles to answer basic questions concerning use, cost effectiveness, and coverage. Data were collected in tandem from vendors and local online systems to track book receipt, item circulation, and overlap between plans. The study period was fiscal year 2005 (July 1, 2004-June 30, 2005) for the approval plan purchasing data, and circulation use data were collected from July 1, 2004, through March 31, 2007, for both UIUC and Penn State. Multiple data points were collected for each title, including author, title, ISBN, publisher, Library of Congress classification number, purchase price, and circulation data. Results of the study measured the cost-effectiveness of each plan by subject and publisher, analyzed similarities and differences in use, and examined the overlap between the two approval plans. The goals were to establish a benchmark for consistently evaluating approval plan profile effectiveness and to provide a reproducible method with baseline data that will allow other libraries to collect comparable data and conduct their own studies.