The data were collected by individual probation officers. Results revealed that the majority of adults on probation in Illinois completed their sentences satisfactorily; they had no technical violations or rearrests during their period of supervision. Offenders convicted of property and drug law offenses, offenders with histories of drug abuse, offenders with prior involvement in the justice system, and offenders in their late teens and early 20's were most likely to be rearrested, have technical violations, and be negatively discharged from probation. In addition, the satisfaction of probation conditions such as payments of supervision fees and fines not only provided the justice system with substantial revenues to supplement taxpayer funding, but also resulted in the recovery of losses by victim through restitution and by the community through court-ordered community service. Most probationers completed the treatment ordered. Findings also indicated that during supervision a substantial portion of probationers experienced improvement in various aspects of their personal lives, including attitudes, employment stability, and family relationships. Figures, tables, and appended instruments and additional results