THE SAMPLE WAS SELECTED FROM NINE METHADONE MAINTENANCE AND SIX DRUG-FREE PROGRAMS IN NEW YORK CITY, WASHINGTON, D.C., CHICAGO, ILL., LOS ANGELES, CALIF., AND SAN FRANCISCO, CALIF. ONE ADDITIONAL PROGRAM HAD BOTH A METHADONE AND A DRUG-FREE UNIT. INTERVIEWS WERE CONDUCTED WITH 82 COUNSELORS, 302 OF THEIR CLIENTS, AND WITH 29 PROGRAMS ADMINISTRATORS. CONSIDERATION WAS GIVEN TO THE LENGTH OF TIME CLIENTS SPENT IN TREATMENT, COUNSELING INPUTS, CLIENT STATUS, AND TREATMENT OUTCOMES (IN TERMS OF DRUG USE, EDUCATION, EMPLOYMENT, PRODUCTIVITY, CRIMINALITY, AND QUALITY OF LIFE). FEW DIFFERENCES WERE FOUND IN CLIENT BACKGROUNDS FOR THE THREE COUNSELOR GROUPS (PROFESSIONAL, EXADDICT, AND NONEXADDICT COUNSELORS). CLIENTS OF PROFESSIONAL COUNSELORS WERE ABOUT 3 YEARS YOUNGER THAN CLIENTS OF NONEXADDICT COUNSELORS. IN THE DRUG-FREE MODALITY, CLIENTS OF PROFESSIONAL COUNSELORS REPORTED SLIGHTLY MORE EXCESSIVE ALCOHOL USE THAN CLIENTS OF NONEXADDICT COUNSELORS AND ALSO HAD APPROXIMATELY ONE MORE TREATMENT EPISODE THAN CLIENTS OF NONEXADDICT COUNSELORS. ABOUT 15 PERCENT MORE CLIENTS OF EXADDICT COUNSELORS THAN CLIENTS OF PROFESSIONAL AND NONEXADDICT COUNSELORS HAD SPENT ANY TIME IN JAIL IN THE YEAR PRIOR TO TREATMENT ENTRY. SUPPORTING DATA AND A BIBLIOGRAPHY ARE INCLUDED. CLIENT BACKGROUND DATA ARE TABULATED IN AN APPENDIX. (DEP)