The General Criminal Thinking (GCT) score of the Psychological Inventory of Criminal Thinking Styles (PICTS) was found to successfully predict institutional adjustment in 2,487 male medium security federal inmates after controlling for eight static risk factors (age, race, confining offense, sentence, gang affiliation, mental health history, substance abuse history, criminal history). Causal mediation analysis was also performed and showed that the GCT score partially mediated the relationship between static risk and total infractions. These results suggest that the GCT score may have a role in internal classification and in clarifying the relationship between static risk factors and prison misconduct.