BENNETT W. FLETCHER's primary work at the National Institute on Drug Abuse has been in developing large-scale longitudinal drug treatment evaluation research, including the Drug Abuse Treatment Outcome Study. He is the co-editor of Innovative Approaches in the Treatment of Drug Abuse (Greenwood, 1993).JAMES A. INCIARDI is director of the Center for Drug and Alcohol Studies and Professor of Sociology and Criminal Justice at the University of Delaware. He is the co-editor of Innovative Approaches in the Treatment of Drug Abuse (Greenwood, 1993), editor of Handbook of Drug Control in the United States (Greenwood, 1990), and author of more than 130 articles, chapters, and books in the areas of criminal justice, substance abuse, history, folklore, criminology, medicine, law, public policy, and AIDS.ARTHUR M. HORTON is a research psychologist/project officer in the Treatment Research Branch of the Division of Clinical Research of the National Institute on Drug Abuse. He has held faculty appointments at the University of Maryland Medical School, Johns Hopkins University, West Virginia University, and the University of Virginia. The author or editor of four books, his most recent contribution was the edited volume Neuropsychology Across the Life-span: Assessment and Treatment (1990).