THE 100 ADDICTS WERE ADMITTED TO SAN ANTONIO, TEX., METHADONE MAINTENANCE PROGRAMS BETWEEN DECEMBER 15, 1971 AND DECEMBER 23, 1971. ALL PATIENTS ENTERED THE PROGRAM VOLUNTARILY. THE STUDY POPULATION WAS 92 PERCENT MALE AND 96 PERCENT MEXICAN-AMERICAN, WITH 84 PERCENT NONGRADUATES OF HIGH SCHOOL. AFTER 1 YEAR, 70 PERCENT WERE RECEIVING METHADONE. THE TOTAL NUMBER OF CRIMINAL CHARGES DECREASED FROM 189 BEFORE ADMISSION TO 129 AFTER ADMISSION. EXCLUDING VAGRANCY, THE REDUCTION IN CRIMINAL CHARGES WAS ONLY 14 PERCENT. IN ONE CATEGORY (BURGLARY AND THEFT), A STATISTICALLY SIGNIFICANT DECREASE OF 40 PERCENT WAS FOUND. ARREST FREQUENCIES WERE GENERALLY CORRELATED WITH OTHER OUTCOME MEASURES SUCH AS EMPLOYMENT STATUS AND CONTINUATION IN METHADONE TREATMENT. THOSE NOT ARRESTED IN THE YEAR BEFORE TREATMENT WERE ONLY HALF AS LIKELY TO BE ARRESTED IN THE YEAR AFTER TREATMENT. THOSE NOT ARRESTED IN EITHER PERIOD HAD MUCH HIGHER RATES OF EMPLOYMENT AND PROGRAM RETENTION. RESULTS SUGGEST THAT (1) METHADONE MAINTENANCE MODESTLY REDUCED BEHAVIOR; (2) METHADONE MAINTENANCE PRODUCED NO SIGNIFICANT REDUCTION IN CRIME NOT DIRECTLY RELATED TO NARCOTICS ADDICTION; AND (3) METHADONE PROGRAM STAFF MAY USE ARREST HISTORY AS A GUIDE TO PROSPECTIVE PROBLEMS WITH WORK, COMPLIANCE WITH PROGRAM REQUIREMENTS, AND ADDITIONAL CRIMINAL ACTIVITY. A FIGURE AND A REFERENCE LIST ARE INCLUDED. (CFW)