Treatment performance is defined as an offender’s involvement in treatment, compliance with treatment rules and expectations, and attainment of treatment goals. Treatment performance can be analyzed as a potential static risk factor or as a potential dynamic risk factor. Static risk factors are defined as those predictors of recidivism that are historical or very unlikely to change, such as prior offense history. Dynamic risk factors are defined as those predictors of recidivism that can change over time, such as peer relationships. A number of studies have examined the relationship between aspects of treatment performance and outcomes among sex offenders. All of these studies examined treatment performance as a potential static risk factor. There is little evidence to support the claim that sex offender treatment performance is a static risk factor, such that good treatment performance is related to lower long-term risk to seriously re-offend among sex offenders. This suggests that adjusting estimates of long-term risk to re-offend based on treatment performance or reporting that a sex offender is lower in risk because of good treatment performance exhibited while participating in a treatment program is not empirically supported. It is still possible that treatment performance is a dynamic risk factor that predicts the imminence of any serious recidivism that might occur among individuals at a given level of long-term risk to re-offend. To establish treatment performance as a dynamic risk factor, more research is needed to determine whether changes in treatment performance are related to problematic behavior and recidivism among sex offenders that are at risk in the community. An important issue for this line of research is to distinguish genuine from simulated treatment performance. 1 table, 3 figures, 2 notes, 55 references