Meta-analyses have suggested that sexual offender treatment (SOT) completion is associated with lowered sexual recidivism rates for convicted sexual offenders. The paucity of properly designed studies allows for the alternative explanation of less recidivism among treated samples as reflecting that lower risk offenders disproportionately self-select into treatment. A test of the "self-selection explanation" can occur by investigating treatment effect on known high-risk offenders. Psychopathy correlates with increased sexual recidivism risk, such that an exploration of the SOT effect on psychopathic offenders could clarify the accuracy of the self-selection hypothesis. Additionally, the debated degree to which psychopaths are treatable might obtain clarification by a research review. This article examines empirical findings concerning the effectiveness of SOT for psychopathic sexual offenders. Ten studies were found to meet the minimal quality standards used, stemming from only four data sources. Shortcomings of existing research precluded clear conclusions, though trends in the data are delineated.