Although more than 12,000 offenders are on parole at any given time, little is known about the effectiveness of parole supervision in reducing reoffending. The few studies that have been conducted involve samples of parolees released from prison in other countries. The present study is the first to evaluate the effectiveness of parole supervision in Australia. It compares several groups of offenders, matched in terms of the factors likely to affect reoffending, but differing in terms of whether they are supervised and if supervised, in terms of the intensity of supervision. The results suggest that parole supervision does reduce the risk of reoffending.