This article is concerned with the capacity of probation supervision to reduce the likelihood of offending among probationers. An increasing number of studies have indicated that probation supervision can be effective, however, that effectiveness is dependent on the particular program'and the characteristics or approach of the supervisor. Some studies in the United States and Canada suggest that a supervisor who is ‘pro-social’ and who presents a pro-social role model will be more effective than a supervisor with a more delinquent or anti-social orientation. This article reports on a study of Victorian volunteer (unpaid) probation officers and their clients. Like the overseas studies, it finds, that pro-social officers are more effective.