Antisocial personality disorder (ASPD) and borderline personality disorder (BPD) are common conditions in forensic settings that present high rates of violence. Personality traits related to the five-factor model personality domains of neuroticism and agreeableness have shown a relationship with physical aggression in nonclinical and general psychiatric samples. The aim of the present investigation was to examine the association of these personality traits with violence and aggression in ASPD and BPD. Results revealed that trait anger/hostility predicted self-reported physical aggression in 47 ASPD and BPD subjects (beta = 0.5, p = 0.03) and number of violent convictions in a subsample of the ASPD participants (beta = 0.2, p = 0.009). These preliminary results suggest that high anger and hostility are associated with physical aggression in BPD and ASPD. Application of validated, self-report personality measures could provide useful and easily accessible information to supplement clinical risk assessment of violence in these conditions.