To present nationally representative findings on prevalence, sociodemographic correlates, disability, and comorbidity of borderline personality disorder (BPD) among men and women. Face-to-face interviews were conducted with 34,653 adults participating in the 2004–2005 Wave 2 National Epidemiologic Survey on Alcohol and Related Conditions. Personality disorder diagnoses were made using the Wave 2 Alcohol Use Disorder and Associated Disabilities Interview Schedule–DSM-IV Version. Prevalence of lifetime BPD was 5.9%(99% CI= 5.4 to 6.4). There were no differences in the rates of BPD among men (5.6%, 99% CI= 5.0 to 6.2) and women (6.2%, 99% CI= 5.6 to 6.9). BPD was more prevalent among Native American men, younger and separated/divorced/widowed adults, and those with lower incomes and education and was less prevalent among Hispanic men and women and Asian women. BPD was associated with substantial mental and physical disability, especially among women. High cooccurrence rates of mood and anxiety disorders with BPD were similar. With additional comorbidity controlled for, associations with bipolar disorder and schizotypal and narcissistic personality disorders remained strong and significant (odds ratios≥ 4.3). Associations of BPD with other specific disorders were no longer significant or were considerably weakened. BPD is much more prevalent in the general population than previously recognized, is equally prevalent among men and women, and is associated with considerable mental and physical disability, especially among women. Unique and common factors may differentially contribute to disorder-specific comorbidity with BPD, and some of these associations appear to be sex-specific. There is a need for future epidemiologic, clinical, and genetically informed studies to identify unique and common factors that underlie disorder-specific comorbidity with BPD. Important sex differences observed in rates of BPD and associations with BPD can inform more focused, hypothesisdriven investigations of these factors.