The use of pro re nata (PRN; as needed) psychotropic medication in patients with borderline personality disorder (BPD) has not been well characterized. This study had 3 purposes, which are as follows: (1) to describe the prevalence of PRN psychotropic medication use among patients with BPD and comparison subjects with other personality disorders (OPD) over 14 years of prospective follow-up, (2) to examine the rates reported by patients with BPD who ever recovered and never recovered, and (3) to examine the reasons for taking PRN medication reported by these patients. Overall, the prevalence of PRN psychotropic medication use was initially approximately 3 times higher among patients with BPD than comparison subjects with OPD, with a significant one-third decline in the use of PRN medication reported by patients with BPD over time. In analyses restricted to patients with BPD, patients with BPD who never recovered were approximately twice as likely to use PRN medication than patients with BPD who ever recovered over time. In reasons for use, the rates of PRN medication use to decrease agitation for both diagnostic groups declined significantly over time, whereas they remained significantly higher among patients with BPD. Likewise, patients with BPD who never recovered reported higher use of PRN medication to decrease agitation than patients with BPD who ever recovered over time. The results of this study indicate that PRN psychotropic medication is widely used for the treatment of patients with BPD, particularly those who have not achieved a recovery in both the symptomatic and psychosocial realms. They also suggest that patients with BPD use proportionally more PRN medication to decrease agitation than comparison subjects with OPD, with lower proportional use to reduce agitation found among recovered patients with BPD.