Daniel O'Leary is a Distinguished Professor of Psychology at Stony Brook University. He is a clinical psychologist who received his B. A. from Penn State University and his Ph.D. from the University of Illinois at Urbana, Illinois. After Illinois, he went directly to Stony Brook where he has been throughout his career and where he served as department chair from 1978-1981 and Director of Clinical Training from 2002-2010.He is in private practice of clinical psychology, specializing in treatment of depression and psychological and physical aggression. He conducts forensic evaluations for child custody, and he provides divorce and relationship mediation with attorney Dawn Murphy. He was editor of the Journal of Applied Behavior Analysis, and he was Associate Editor of the Journal of Abnormal Child Psychology. He is or has been on other editorial boards such as Journal of Consulting and Clinical Psychology, Behavioral Therapy, Behavioral Assessment, Journal of Interpersonal Violence, Journal of Family Violence, and Journal of Family Psychology. He is a Fellow of the American Psychological Association (Divisions 7, 12, and 25). He was president of the American Association for Advancement of Behavior Therapy.He is author or co-author of thirteen books, and his most recent books are Understanding Psychological and Physical Aggression in Couples: Existing Evidence and Clinical Implications (with Erica Woodin, 2009), and Couples Psychotherapy Treatment Planner, (2nd Ed, 2011, with Richard Heyman and Arthur Jongsma). He has published 275 manuscripts in edited journals, and he was among the top 100 cited psychologists in the English-speaking world. He received the Distinguished Scientist Award from the clinical division (12, Section III) of the American Psychological Association in August, 1985. He was installed to the National Academies of Practice in Psychology on August 21, 1986.