A RANDOM SAMPLE OF 193 RESIDENTS WAS DRAWN FROM THE IDENTIFICATION NUMBERS OF THE 1,420 PERSONS WHO ENTERED THE ILLINOIS PROGRAM FROM JULY 1968 TO JUNE 1974. THREE GROUPS WERE STUDIED: GROUP 1, PERSONS WHO DROPPED OUT OF TREATMENT WITHIN THE FIRST 9 MONTHS (89 SUBJECTS, MEAN TIME IN TREATMENT OF 3 MONTHS); GROUP 2, THOSE WHO REMAINED IN TREATMENT 9 MONTHS OR MORE BUT WHO, IN THE OPINION OF CLINICAL STAFF, LEFT PREMATURELY (70 SUBJECTS, MEAN TIME IN TREATMENT OF 16.5 MONTHS); AND GROUP 3, THOSE WHO COMPLETED TREATMENT (34 WITH A MEAN TIME IN TREATMENT OF 27.6 MONTHS). THE GROUPS WERE COMPARABLE DEMOGRAPHICALLY, WITH TOTALS OF 64.5 PERCENT WHITE, 28.7 PERCENT BLACK, AND 6.2 PERCENT SPANISH SURNAMED. AVERAGE AGE AT ADMISSION WAS 23; AND 72.5 PERCENT WERE MALE. GROUP 1 SHOWED NO CHANGE IN ARREST RATES FROM THE YEAR PRIOR TO ADMISSION TO THE YEAR FOLLOWING DISCHARGE. GROUP 2 HAD AN 81 PERCENT REDUCTION IN ARREST RATES, AND GROUP 3 A 97 PERCENT REDUCTION. THE GREATEST DROP WAS IN ARRESTS FOR DRUG RELATED CRIMES, ALTHOUGH SIGNIFICANT REDUCTIONS WERE ALSO FOUND FOR THEFT AND DISORDERLY CONDUCT. A SIGNIFICANTLY GREATER NUMBER OF THOSE WHO STAYED IN THE PROGRAM ENTERED UNDER SOME FORM OF LEGAL PRESSURE, AND IT IS ARGUED THAT THE COURTS PROVIDED MOTIVATION UNTIL THE PERSON COULD ACCEPT THE PROGRAM GOALS PERSONALLY. TABLES ANALYZE THE STUDY DATA WHILE REFERENCES ARE APPENDED. (GLR)