Returning to Maryland, Kirwan accepted an offer on March 25, 2002, to become chancellor of the University System of Maryland (USM). Kirwan began as chancellor on August 1, 2002. In 2009, he received the Carnegie Corporation Leadership Award, which included a $500,000 grant for academic programs. The following year, Kirwan won the 2010 TIAA-CREF Theodore M. Hesburgh Award for Leadership Excellence. On May 13, 2014, Kirwan announced publicly that he would step down as USM chancellor after twelve years of service. As a tenured member of the Mathematics faculty at the University of Maryland, College Park, he will serve as the Regents Professor of Mathematics. Kirwan retired effective June 30, 2015, and was succeeded by Robert Caret. In October 2015, University of Maryland, College Park named its mathematics building William E. Kirwan Hall in Kirwan's honor. Other service College athletics Kirwan has also had executive-level positions relating to college athletics, including with the National Collegiate Athletic Association (NCAA). In addition to serving on the NCAA's Executive Committee and Committee on Agents and Amateurism, Kirwan chaired the NCAA Division I Board of Directors from 2000 to 2003. In May 2006, Kirwan joined the Knight Commission on Intercollegiate Athletics. From April 2007 to December 31, 2015, Knight co-chaired the Knight Commission; he served as sole chair for the entire 2016 calendar year before retiring. In 2010, as the NCAA conference realignment was about to begin, the Knight Commission released a report calling on the NCAA and its member schools to reform their financial and academic practices. According to the report, from 2005 to 2008, spending on major college athletic programs increased by an average of 38 percent, compared to a growth of 20 percent for their colleges' academic spending. Kirwan stated: "There is every reason to believe that the direction the major programs are headed in will lead to further escalation in athletics spending and even greater imbalances in the fiscal priority for athletics over academics." The Knight Commission report made several recommendations: NCAA member schools should include more details comparing athletic and academic spending in financial reports that are filed with the NCAA. The NCAA should strengthen its Academic Progress Rate standard to give postseason bans following a single year's unsatisfactory score, in contrast to the NCAA's established standard of a three-year average, Schools with APR scores that reflect a graduation rate of 50 percent or more should get financial bonuses