THE DARP WAS ESTABLISHED TO CREATE A DATA BASE FOR RESEARCH ON THE EVALUATION OF DRUG-ABUSE TREATMENT. BETWEEN JUNE 1969 AND APRIL 1973, THIS PROGRAM RECORDED APPROXIMATELY 44,000 ADMISSIONS TO TREATMENT AT 52 AGENCIES LOCATED THROUGHOUT THE UNITED STATES AND IN PUERTO RICO. THESE DATA HAVE BEEN ANALYZED IN RELATION TO OUTCOME DURING TREATMENT, AND MORE RECENTLY, IN CONJUNCTION WITH FOLLOWUP STUDIES OF SAMPLES OF 1969-1971 AND 1971-1972 ADMISSIONS IN RELATION TO POSTTREATMENT OUTCOMES. TWO DATA SETS ARE ANALYZED IN THE PRESENT STUDY. THE FIRST CONSISTED OF 5,405 BLACK AND WHITE YOUTHS AGE 19 YEARS AND UNDER DRAWN FROM THE DARP FINAL RESEARCH TAPE. THE SECOND INCLUDED 587 BLACK AND WHITE YOUTHS WHO WERE INTERVIEWED IN THE DARP COHORT 1 AND COHORT 2 FOLLOWUP STUDIES; PUERTO RICAN AND MEXICAN-AMERICAN YOUTHS WERE EXCLUDED BECAUSE OF INSUFFICIENT NUMBERS. THE DATA SOURCE IS DESCRIBED, AND THE DARP DATA SYSTEM, THE TREATMENTS PROVIDED, THE TREATMENT POPULATION, AND THE CHARACTERISTICS OF THE YOUTHS IN TREATMENT ARE REVIEWED, FOLLOWED BY A SUMMARY OF RETENTION AND TERMINATION DATA FOR A YOUTH SAMPLE OF BLACK AND WHITE DARP ADMISSIONS AGE 19 YEARS AND UNDER. NEW POSTTREATMENT FOLLOWUP RESULTS ARE PRESENTED, BASED ON 587 BLACK AND WHITE YOUTHS WHO WERE INTERVIEWED 1 TO 6 YEARS AFTER TERMINATION FROM DARP. THE POSTTREATMENT DATA SUPPORT THE CONCLUSION THAT THE DRUG-FREE TREATMENTS IN DARP WERE MOST EFFECTIVE FOR THE YOUTHS ASSIGNED TO THEM. BY COMPARISON, THE SMALL CONTROL GROUP HAD THE POOREST RECORD. OUTCOMES WERE POOR, HOWEVER, IN REDUCING THE USE OF MARIHUANA AND ALCOHOL. THE RECORD IN THESE AREAS PROBABLY REFLECTS DARP PROGRAMS' TARGETING OF THE USE OF HARD DRUGS. SUPPORTING TABULAR DATA AND REFERENCES ARE PROVIDED. (RCB)