Objective: Borderline personality disorder (BPD) is a common personality disorder, with a population prevalence of 1.4-5.9%, although the epidemiology of this disorder in primary care is insufficiently known. Our objective was to determine the registered prevalence of BPD in primary care databases and to study the demographic and clinical characteristics of these patients. Methods: We performed a cross-sectional study of the computerized databases of primary care clinical records. The target population consisted of all adults (≥ 16 years old) registered in the Catalan Health Institute (n = 4,764,729). Results: The prevalence of recorded BPD was 0.017%, and was higher in patients with other mental disorders, particularly substance-abuse disorders (0.161%). These patients had twice as many appointments with the general practitioner as the general population (8.1 vs. 4.4). Conclusion: The number of diagnoses of BPD recorded in primary care is extremely low, which contrasts with the available population-based data.