In order to identify genetic factors explaining inter-individual differences in personality, we studied the association between a polymorphism in the serotonin transporter (SERT) gene known as 5HTTLPR (Serotonin transporter-linked promoter region) and one in the brain-derived neurotrophic factor (BDNF) gene (G196A, or Val66Met, rs6265), with FFM personality traits, in a sample of 76 individuals with borderline personality disorder (BPD). The gene discussed is BDNF; the disease is Borderline personality disorder.