This is a prospective clinical, epidemiological study of clients who entered drug-abuse treatment programs from 1979 to 1981. During the course of TOPS, 11,182 clients were interviewed at admission to drug-abuse treatment by program researchers hired to work in assigned clinics and professionally trained and supervised by Research Triangle Institute (RTI) field staff. The interviews at admission covered demographics, history of drug use, treatment, arrest and employment behavior in the year prior to treatment, and status upon admission to treatment. The study was sponsored by the NATIONAL INSTITUTE ON DRUG ABUSE (NIDA) and by the RTI. The study population included 4,184 clients from 12 outpatient methadone programs, 2,891 clients from 14 residential programs, and 2,914 clients from 11 outpatient drug-free programs in 10 cities. Interviews with questions on behavior, services received, and satisfaction were collected by the program researchers every three months while clients remained in treatment. The self-report data...