The study found that measures of executive functioning predicted a large part of the variance for both outcome variables and were the only variables that predicted changes in positive behavior. Regarding change in negative behavior, the variable most predictive of improvement was the number of previous convictions. This was closely followed by two measures of executive function and by age. It is possible that change in positive behavior is predicted only by measures of executive functioning, since the Behavior Rating Scale (BRS), which was used in this study, measures positive behavior in terms of observed problem-solving behavior. This may be viewed as an aspect of executive functioning. Change in negative behavior, on the other hand, is a broader concept that includes factors linked with poor executive functioning, such as impulsivity, social withdrawal, and emotional distress. The measures of executive functioning most predictive of improvements in problem-solving behavior were the ability to shift one's focus of attention and planning ability. The ETS course, which is designed for use with medium-risk violent and aggressive offenders, consists of 20, 2-hour sessions conducted over 5 weeks, with additional follow-up work. Sessions include practical tasks, role play, games, and group discussion, all based around core themes. These themes include problem-solving, decisionmaking, the relationship between thoughts, emotions and behavior, and social skills. Offenders due to undergo ETS (n=42) were assessed with a battery of neuropsychological measures of executive functioning and other psychometric instruments. Change in behavior following ETS was assessed with the BRS. Post-ETS changes in the positive and negative scales of the BRS were the independent variables in two separate analyses. 5 tables and 48 references