A.Thomas McLellan, Ph.D. is the CEO and co-founder of the Treatment Research Institute (TRI) and an experienced substance abuse researcher. From 2009 to 2010, he was Science Advisor and Deputy Director of the White House Office of National Drug Control Policy (ONDCP), a congressionally confirmed Presidential appointment to help shape the nation’s public policy approach to illicit drug use. At ONDCP, McLellan worked on a broad range of drug issues, including formulation and implementation of the President’s National Drug Control Strategy and promotion of drug treatment through the broader revamping of the national health care system. Dr. McLellan has more than 35 years of experience in addiction treatment research. In 1992, he co-founded and led TRI (until his ONDCP appointment) to transform the way research is employed in the treatment of and policy making around substance use and abuse. In his career he has published over 400 articles and chapters on addiction research. From 2000-2009 he was Editor-in-Chief of the Journal of Substance Abuse Treatment, and he has also served on several other editorial boards of scientific journals. Dr. McLellan is the recipient of several distinguished awards including the Life Achievement Awards of the American and British Societies of Addiction Medicine (2001 & 2003); the Robert Wood Johnson Foundation Innovator Award (2005); and awards for Distinguished Contribution to Addiction Medicine from the Swedish (2002) and Italian (2002) Medical Associations. In the 1980s, with his colleagues from the Center for the Studies of Addiction at the University of Pennsylvania, Dr. McLellan introduced the Addiction Severity Index and, later, the Treatment Services Review. Both are among the most widely used assessment instruments in the world.