The study involved semi-structured interviews with 21 probation officers and 60 of their probationers, conducted between July and October 1994. A unifying theme in the remarks of probationers who attributed changes in their behavior to their supervisory experiences was the active and participatory nature of those experiences. Supervisory monitoring, in and of itself, was not a factor in behavioral change; rather, the quality of the monitoring in terms of assisting probationers to deal with problems and difficulties was the key ingredient in behavioral change. Supervision and services that were particularly helpful in behavioral change were those that improved probationers' reasoning and decision making, those that strengthened social ties, those that reinforced prosocial behavior, and those that established the probation officer's moral authority and legitimacy. The latter quality in probation officers motivates probationers to avoid reoffending out of a desire to meet probation officers' expectations, which are perceived by the probationer as being in his/her best interests. The weakness in most probation officers' supervisory style was their failure to recognize, appreciate, and deal with the impediments and circumstances that make it so difficult for many probationers to change their behaviors and lifestyles. 4 notes and 52 references