Estimates of the probabilities of rearrest for sex offenders apprehended (n=2,785) in Western Australia between 1984 and 1994 are reported. Subjects on average were followed up for 5.7 years and assessed by criminal record, Aboriginality, bail status, age, occupation and penal intervention. Three criteria, rearrest for any, repeat sex or a violent offence are used to summarise the ‘careers’ of sex offenders. Overall ultimate probabilities of rearrest for any offence were 0.61, for a repeat sex offence 0.33 and for a violent offence 0.51. Probabilities of rearrest for non-Aboriginal offenders were lower for all definitions. Younger offenders, Aborigines and those with prior arrest for non-sex offences had higher probabilities for any or violent rearrest but older offenders tended to have higher probabilities of repeat sex offending. Community supervision and imprisonment significantly reduced the ‘rate’ or speed of rearrest. The utility of actuarial risk assessment for low probability high consequence events such as dangerous recidivism and the evaluation of penal interventions for criminal justice policy are discussed
