Each year, substance abuse treatment programs in the United States record approximately 150,000 admissions of youths under the age of 18. Nevertheless, little is known about the effectiveness of the types of community-based services typically available to youths and their families. Recognizing the need for better information on the effectiveness of adolescent treatment services, the Substance Abuse and Mental Health Services Administration, Center for Substance Abuse Treatment (SAMHSA/CSAT) established the Adolescent Treatment Models (ATM) program. ATM grants were available to established adolescent treatment programs with at least suggestive evidence of effectiveness. These grants supported an independent, longitudinal evaluation of the client outcomes. Eleven such studies were funded in 1998 and 1999, each of which used parallel data collection instruments and study designs (see Stevens & Morral, 2003, for discussion of the 11 programs and each site's study design). After the Preface; Figures; Tables; Summary; Acknowledgments and Abbreviations, the book is divided into seven chapters: (1) Introduction; (2) The ATM Programs; (3) Case-Mix Adjustment Approach; (4) Study Procedures; (5) Case-Mix Adjusted Comparison Samples; (6) Outcomes; and (7) Discussion. Supporting tables are appended. (Contains 14 figures and 19 tables.) [This report was prepared for the Substance Abuse and Mental Health Services Administration, Center for Substance Abuse Treatment. The research described in this report was carried out under the auspices of the Drug Policy Research Center, a joint endeavor of RAND Infrastructure, Safety, and Environment (ISE) and RAND Health.]