Anger and aggression are typical in borderline patients. The goal of this study was to compare the efficacy of lamotrigine versus placebo in the treatment of aggression in women meeting the criteria for borderline personality disorder (BPD). We conducted a randomized, double-blind, placebo-controlled study of lamotrigine in 24 female subjects meeting Structured Clinical Interview for DSM-IV (SCID) criteria for BPD. The subjects were randomly assigned in a 2: 1 manner ratio to lamotrigine (n = 18) or placebo (n = 9). Treatment duration was 8 weeks. Primary outcome measures were self-reported changes on the anger scales of the Trait Anger Expression Inventory (STAXI). In comparison with the placebo group, and according to the intention-to-treat principle, highly significant (p < 0.01) changes on four STAXI scales (State-Anger, Trait-Anger, Anger-Out, Anger-Control) were observed in those subjects treated with lamotrigine after 8 weeks. The only exception (p < 0.05) was found on the Anger-In scale, where a difference of only 8.5% (p < 0.2) was found. All the patients tolerated lamotrigine relatively well. Lamotrigine appears to be a safe and effective agent in the treatment of anger in women with criteria-defined BPD as defined by SCID criteria. It did not produce any clinically significant effect on body weight.