THIS IS THE FIRST REPORT ON THE POSTTREATMENT STATUS OF COHORT 1 (POPULATION RESTRICTED TO DAILY HEROIN AND OTHER OPIOID USERS) OF THE NATIONALLY ORIENTED NATIONAL INSTITUTE OF DRUG ABUSE-TEXAS CHRISTIAN UNIVERSITY DRUG ABUSE REPORTING PROGRAM RESEARCH ON THE EFFECTIVENESS OF TREATMENT FOR DRUG ABUSE. IT IS CONSIDERED A PRELIMINARY REPORT SINCE THE FIELD WORK WAS COMPLETED WITHIN THE MONTH PRIOR TO THIS REPORT. COHORT 1 CONSISTED OF 11,383 CLIENTS WHO HAD BEEN ADMITTED TO 23 TREATMENT AGENCIES BETWEEN JUNE 1, 1969 AND MAY 31, 1971. OF THE TOTAL SAMPLE, 9,574 WERE ELIGIBLE FOR INCLUSION IN THE FOLLOWUP STUDY. OF THE 87 PERCENT LOCATED AND INTERVIEWED FOR FOLLOWUP, RESULTS ARE REPORTED FOR A SUBSAMPLE OF 1,078 BLACK AND WHITE MALES. THE OUTCOME CRITERIA MEASURED INCLUDE A NUMBER OF BEHAVIORAL MEASURES OF OPIOID DRUG USE, ALCOHOL USE AND PROBLEMS, CRIMINALITY, GAINFUL EMPLOYMENT, AND RETURN TO TREATMENT. THE PROGRAM TYPES REPRESENTED IN THE SUBSAMPLE INCLUDE TWO DISTINCT TYPES OF METHADONE MAINTENANCE TREATMENT (MM), THREE TYPES OF THERAPEUTIC COMMUNITY (TC), TWO TYPES OF OUTPATIENT DRUG-FREE TREATMENT (DF), INPATIENT (DT-IP) AND OUTPATIENT (DT-OP) DETOXIFICATION, AND A NO-TREATMENT (NT) GROUP. DATA WERE GATHERED FOR THREE TIME PERIODS: PRETREATMENT (2 MONTHS PRECEDING TREATMENT); SINCE TERMINATION (FROM TREATMENT TERMINATION TO INTERVIEW--1 TO 6 YEARS); AND AT INTERVIEW (2-MONTH PERIOD ENDING WITH THE DATE OF THE INTERVIEW). RESULTS SHOWED THAT THE TWO MAJOR MODALITIES, MM AND TC, HAD CLEARLY SUPERIOR OUTCOMES TO THE DT-OP AND NT GROUPS ON MOST COMPARISONS, BUT THE DT AND NT CLIENTS HAD HIGHER RATES OF RETURN TO TREATMENT AND ALSO SHOWED IMPRESSIVE CHANGES. OF THE SUBJECTS, 61 PERCENT RETURNED TO TREATMENT AND 25 PERCENT REPORTED LIVING WITH REGULAR DRUG USERS AFTER LEAVING TREATMENT, INDICATING THAT DESPITE REDUCTION OF DRUG USE AND SOME SUCCESS IN FINDING JOBS, MANY CLIENTS CONTINUE TO HAVE CLOSE TIES WITH THE DRUG CULTURE. TABULAR DATA ARE REPORTED. (RCB)