In England and Wales, reconviction rates have been the standard measure used to indicate the success or failure of offenders following their participation in a custodial or community-based treatment program. However, in the criminological and psychological literature, the terms reconviction, reoffending, and recidivism have been used interchangeably. This study aimed to assess other offense-related outcomes for sexual offenders, in addition to reconviction, which includes reoffending and recidivism. The study identified a regional area, the Thames Valley Project (TVP) which records a broad range of offending or offense-related behaviors for a group of sexual offenders. TVP is a community-based assessment and treatment provision working with male, adult sexual offenders across Oxfordshire, Buckinghamshire, and Berkshire. The study sample consisted of 173 sexual offenders who had completed treatment with TVP between July 1995 and May 1999 with follow-up to the end of May 2001. This study indicates that collecting evidence of sexual recidivism both improves on the base rate of sexual reconviction and provides a more accurate measure of offense-related sexual behavior displayed by sexual offenders. It also suggests how reconviction rates can be used to estimate the level of recidivism in the same sample. By broadening the outcome measure of treatment programs for sexual offenders, a better indicator of the true level of success or failure by the participants post-treatment is given. References