Borderline personality disorder (herein referred to as BPD) is commonly a lifelong affliction, associated with high utilization of psychiatric and non-psychiatric health services, usually initially manifest by young adulthood and persistent throughout the lifespan. However, clinical recovery is possible for many BPD patients with appropriate psychiatric care. Many others, however, especially those patients with poor treatment engagement, continue to suffer various psychiatric morbidities throughout life. The specific symptoms and behaviors can change over time and understanding of the evolution of this disorder and its clinical manifestations over time are important in order to properly identify, treat, and serve these patients. The clinical diagnostic criteria for BPD have also evolved over time, but specific considerations of BPD in older adults have yet received little attention in the medical literature. This chapter illustrates the general principles of BPD, history of the diagnosis, and the clinical characteristics and associated risks for disruptive life events in older patients with BPD. Although descriptions in this text primarily pertain to older adults with BPD who are admitted or residing in institutional settings, many of these principles are also applicable to those who are living in the community. Unless otherwise specified, "geriatric" and "older adults" will refer to those aged 65 years or older.