Of 483 inmates who were referred to a sex offender treatment program and followed for an average of 44 months of opportunity to reoffend, 38% were arrested for new violent or sexual offenses. Treated offenders were most frequently rearrested for sex offenses. Inmates judged unsuitable for treatment were rearrested less frequently, particularly for sex offenses. Inmates judged to not require treatment and those who refused treatment also had fewer rearrests for sex offenses than did treated participants, although they had more rearrests for violent offenses. After statistically controlling for the static variables that predicted reoffending, the treatment program was associated with a higher rate of sexual rearrests but had no effect on the composite variable, violent or sexual rearrests. Among treated offenders, clinical assessment of treatment gains was not significantly associated with recidivism.