The National Treatment Improvement Evaluation Study (NTIES) is a Congressionally-mandated five-year study of the impact of drug and alcohol treatment on thousands of clients in hundreds of treatment units that received public support from the U.S. Department of Health and Human Services (HHS), Substance Abuse and Mental Health Services Administration (SAMHSA), Center for Substance Abuse Treatment (CSAT). The CSAT-commissioned study was conducted by the National Opinion Research Center, University of Chicago, in conjunction with Research Triangle Institute. The full report provides a wealth of data useful in improving today's treatment programs and in designing new programs to advance treatment in the future. The "Methodology" section, found in the Appendix, contains information about study design and detail about participants. The information reported here was gathered from 4,411 clients from across the country. It includes clients who completed an intake interview and returned for at least a single visit. Since these people did not really become involved in treatment, their inclusion in the study may lower the overall estimates of the success of treatment. Substance abuse is a chronic relapsing disease and the NTIES study reflects that not everyone who enters treatment completes it. The individuals served by CSAT grants were from vulnerable and underserved populations (minorities, pregnant women and at-risk women, youth, public housing residents, welfare recipients, and those in the criminal justice system), and may also have been the most difficult to treat. NTIES Table of Contents | Introduction | Conclusions | Appendix | NTIES Findings on: Drug and Alcohol Use | Changes in Criminal Behavior | Employment, Income, and Homelessness | Changes in Physical and Mental Health | Changes in Sexual Behavior | Variation in Treatment Outcomes | Costs of Treatment