Borderline personality disorder (BPD) is a complex psychiatric disorder characterized by pervasive instability in emotional regulation, self-image, interpersonal relationships, and impulse control (Skodol et al., Biol Psychiatry. 51:951–63, 2002). Between 1% and 6% of adults meet the diagnostic criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) (Lenzenweger and Willett, J Abnorm Psychol. 116:684–700, 2007). BPD is the most common personality disorder among psychiatric patients, with a prevalence ranging from 10% in outpatient populations to 15%–25% in hospitalized patients (Gunderson, Am J Psychiatry. 166:530–9, 2009). BPD is associated with substantial mental and physical disabilities (Grant et al., J Clin Psychiatry. 69:533–45, 2008). Furthermore, BPD exhibits high and heterogeneous patterns of comorbidity with other psychiatric and substance abuse disorders (Eaton et al., Psychol Med. 41:1041–50, 2011), which are identified as strong and significant predictors of regular drinking before sex (Thompson et al., Drug Alcohol Depend. 141:167–70, 2014). However, no study has examined the relationship between BPD and regular alcohol consumption before sex in the general population of the United States or other countries.