The criminal arrest histories of 262 medium-security male inmates were correlated with the Proactive (P) and Reactive (R) composite scales of the Psychological Inventory of Criminal Thinking Styles (PICTS). As predicted, only scores on the P scale correlated significantly with prior arrests for proactive aggression (robbery, burglary) and only scores on the R scale correlated significantly with prior arrests for reactive aggression (assault, domestic violence) when age, education, race, and marital status were controlled in a series of negative binomial regression analyses. The P and R scales also predicted the total number of arrests received by participants in this sample after these same four demographic measures were controlled. The implications of these results for the construct validity of the PICTS composite scales and for matching offenders to interventions are discussed. (Contains 2 notes and 4 tables.)