Drug-Abuse Treatment Outcomes Study (DATOS) is a prospective study designed to determine the outcomes of adult drug abuse treatment delivered in typical, stable, community-based programs and to provide comprehensive information on continuing and new questions about the effectiveness of drug abuse treatment for adults currently available in a variety of publicly funded and private programs. The study examined the role of treatment outcomes and program type, client characteristics (including dependence, treatment history, and physical and mental health comorbidities), treatment received (e.g., length and intensity of services provided), therapeutic approaches, provision of aftercare, and research on the components of effective treatment, including factors that engage and retain clients in programs. Four types of programs were included: outpatient methadone (OPM), short-term inpatient (STI), long-term residential (LTR), and outpatient drug-free (ODF). Respondents were sampled from among adults admitted to drug abuse treatment programs in 11 representative U.S. cities during 1991-1993. Clients entering treatment completed two comprehensive intake interviews (Intake 1 and Intake 2), approximately one week apart. This information is provided in Parts 1 and 2 of the data collection. These interviews were designed to obtain baseline data on drug use and other behaviors, as well as information on background and demographic characteristics, patterns of dependence, living situation and child custody status, education and training, income and expenditures, and HIV risk behaviors, along with assessments of dependence, mental health, physical health, and social functioning. Data on criminal justice status and criminal behavior are reported in Part 5, Illegal Activities Data, and are drawn from the Intake 1 interview. Data reflecting during-treatment progress, including service delivery and client satisfaction, were collected in the one-, three-, and six-month in-treatment interviews (Parts 3, 4, and 8). The 12-Month Post-Treatment Follow-Up Interview (Part 6) replicated many of the intake questions and focused on key behaviors in the year following treatment. Part 7 includes variables for time in treatment and interview availability indicators. The 12-Month Follow-Up Urine Result data (Part 9) provide the results from urine sample tests that were given to a sample of subjects at the time of the 12-Month Follow-Up Interview. Urine specimens were tested for eight categories of drugs (amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine metabolite, methaqualone, opiates, and phencyclidine). The drugs covered in the study were alcohol, tobacco, marijuana (hashish, THC), hallucinogens or psychedelics such as LSD, mescaline, and PCP, cocaine (including crack), heroin, narcotics or opiates such as morphine, codeine, Demerol, Dilaudid, and Talwin, downers or depressants such as sedatives, barbiturates, and tranquilizers, amphetamines or other stimulants such as speed or diet pills, and other drugs. Part 10 contains data for 1393 clients who were interviewed 5 years post treatment. This part contains many of the same types of questions asked during previous interviews.