Objective: Clinical experience suggests a growing prevalence of borderline personality disorder in aged residential care and psychiatric facilities with attendant difficulties in their management. This paper reviews the literature concerning the prevalence, phenomenology and diagnosis of borderline personality disorder in old age. The aim is to elucidate the phenomenological differences in old age and thus improve identification of the disorder. Methods: A systematic search was conducted using MEDLINE, PubMed, EMBASE and PsycINFO databases, employing the search terms including 'personality disorder', 'borderline personality disorder', 'aged care', 'gerontology', 'geriatric psychiatry' and 'life span'. The search included articles in English involving participants 65+ years. Long-term prospective studies of borderline personality disorder, long-term follow-up studies and studies involving older adults from 50+ years were also examined. Results: There is a paucity of literature on borderline personality disorder in the elderly. No diagnostic or rating instruments have been developed for borderline personality disorder in the elderly. The phenomenology of borderline personality disorder in the aged population differs in several respects from that seen in younger adults, causing some of the difficulties in reaching a diagnosis. Escalations of symptoms and maladaptive behaviours usually occur when the diagnosis of borderline personality disorder is either not made or delayed. Improved identification of borderline personality disorder in older patients, together with staff education concerning the phenomenology, aetiology and management of these patients, is urgently needed. Conclusion: Diagnostic instruments for borderline personality disorder in the elderly need to be developed. In the interim, suggestions are offered concerning patient symptoms and behaviours that could trigger psychiatric assessment and advice concerning management. A screening tool is proposed to assist in the timely diagnosis of borderline personality disorder in older people. Timely identification of these patients is needed so that they can receive the skilled help, understanding and treatment needed to alleviate suffering in the twilight of their lives.