Reactive aggression (RA) refers to angry responses to provocation or frustration, while proactive aggression (PA) denotes nonemotional, instrumental, and unprovoked aggression. The current study examined personality-related and cognitive correlates of both aggressive types. Respectively, the predictive values of antisocial personality disorder (ASPD), and of hostile interpretation bias, which is the tendency to interpret ambiguous stimuli in a hostile manner, were studied. The sample consisted of n = 37 male adult patients with mixed diagnoses and n = 29 male nonpatients that responded to vignettes and pictures of ambiguous situations, using both open and closed answer formats. ASPD was assessed by means of the Structured Clinical Interview for DSM-IV Axis II disorders (SCID-II), and the Reactive Proactive Questionnaire (RPQ) measured RA and PA. Results showed that although both RA and PA types were predicted by ASPD traits, RA was additionally predicted by a hostile interpretation bias. These findings suggest that reducing hostile bias is a promising avenue for clinical treatment of ASPD-patients high in RA.