The aim of this study was to examine the effectiveness of good behaviour bonds in reducing re-offending. Data on 19,478 individuals who received a good behaviour bond under section 9 of the Crimes (Sentencing Procedure) Act 1999 (NSW) for their principal offence were examined. Propensity score matching techniques were used to match offenders who received a bond of less than 24 months with offenders who received a bond of 24 months or more. These two matched groups were then compared on time to first new offence. After matching offenders on a large range of factors, time to reconviction was longer for offenders placed on bonds 24 months or longer compared with offenders placed on shorter bonds. A significant effect of bond length on re-offending was apparent for both supervised and unsupervised orders. The evidence presented here tentatively suggests long bonds are more effective in reducing re-offending than short bonds.