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 PROGRAM ADMINISTRATORS. FEW DIFFERENCES WERE OBSERVED AMONG COUNSELOR GROUPS (PROFESSIONAL, EXADDICT, AND NONEXADDICT COUNSELORS). ALL GROUPS WERE FAVORABLY DISPOSED TOWARD CLIENTS. NEITHER THE DRUG AND STREET EXPERIENCE OF EXADDICT COUNSELORS NOR THE PERCEIVED INTELLECTUAL ADVANTAGE OF PROFESSIONAL COUNSELORS WERE ACCURATE PREDICTORS OF COUNSELING EFFICIENCY. NONEXADDICT COUNSELORS SEEMED TO FARE AS WELL WITH CLIENTS AS THE OTHER TWO GROUPS. COUNSELORS INDICATED THEIR WILLINGNESS TO HELP AND TO INTERVENE IN VARIOUS SITUATIONS, AND CLIENTS GENERALLY PERCEIVED THIS. OVERALL, CLIENTS WERE EXTREMELY POSITIVE IN THEIR DESCRIPTIONS OF COUNSELORS. COUNSELORS WERE SEEN AS OPENMINDED AND SUPPORTIVE INDIVIDUALS. SUPPORTING DATA AND A BIBLIOGRAPHY ARE INCLUDED. CLIENT BACKGROUND DATA ARE TABULATED IN AN APPENDIX. (DEP)