Research studies have determined that proactive or instrumental aggression correlates with positive outcome expectancies for violence, whereas reactive aggression correlates with hostile attribution biases. It was hypothesized that the Problem Avoidance factor scale of the Psychological Inventory of Criminal Thinking Styles (PICTS) would serve as an effective proxy for reactive criminal thinking and that the PICTS Self-Assertion/Deception factor scale would serve as an effective proxy for proactive criminal thinking. These two factor scales were subsequently correlated with positive outcome expectancies for crime (n = 313) and a three-item index of hostile attribution bias (n = 164) in a sample of male medium security prison inmates. As expected, the Problem Avoidance scale successfully predicted future hostile attribution biases but not positive outcome expectancies for crime, whereas the Self-Assertion/Deception scale successfully predicted future positive outcome expectancies for crime but not hostile attribution biases. (Contains 3 tables and 3 notes.)