The present study sought to quantify the generalizability of clinical trial results in individuals with a Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM–IV) diagnosis of borderline personality disorder (BPD) to a large representative community sample. Data were derived from the 2004–2005 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a large nationally representative sample of 34,653 adults from the United States population. We applied a standard set of exclusion criteria representative of pharmacological and psychotherapy clinical trials to all adults with a DSM–IV diagnosis of BPD (n = 2,231). Our aim was to assess how many participants with BPD would not fulfill typical eligibility criteria. We found that more than 7 of 10 respondents in a typical pharmacological efficacy trial and more than 5 of 10 participants in a typical psychotherapy efficacy trial would have been excluded by at least 1 criterion. Having a current history of alcohol or drug use disorder and a lifetime history of bipolar disorder explained a large proportion of ineligibility in both pharmacological and psychotherapy efficacy trials. Clinical trials should carefully consider the impact of exclusion criteria on the generalizability of their results. As required by CONSORT guidelines, reporting exclusion rate estimate and reasons of eligibility should be mandatory in both clinical trials and meta-analyses. As treatment trials of borderline personality disorder move from efficacy to effectiveness to better inform clinical practice, the eligibility rate must be increased by imposing less stringent eligibility criteria to allow for more generalizable results.