Complex post-traumatic stress disorder (CPTSD) has been both proposed and disputed as a valid and useful clinical syndrome. CPTSD was originally defined as a disorder of extreme stress not otherwise specified (DESNOS) following traumatic victimisation with symptoms in six domains: (1) emotion dysregulation; (2) altered schemas of self; (3) altered relationships; (4) trauma-related sustaining beliefs (morality, spirituality); (5) somatisation; and (6) altered perceptions of perpetrators. The Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) and International Classification of Diseases, 10th revision (ICD-10) were insufficient to capture the range and diversity of symptoms experienced by trauma- exposed populations, particularly in those who experienced prolonged or chronic trauma. The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) has expanded to include ���negative adaptations in mood and cognitions��� as well as a dissociative subtype. The International Classification of Diseases, 11th revision (ICD-11) has introduced a new diagnosis, CPTSD, which includes the symptoms of ICD- 11 PTSD as well as symptoms representing disturbances in self-organisation (DSO), the latter of which has been demonstrated to be associated with early life and chronic trauma. While initial evidence suggests that CPTSD is distinguishable from a borderline personality disorder (BPD), additional investigations using other methodological approaches such as network analysis are needed to assess the discriminability of CPTSD from BPD and other disorders. This presentation summarises current clinical and scientific findings regarding comorbidity, clinical phenomenology of CPTSD and attempts to address the question of what to do with the entity called CPTSD. Is it a distinct disorder from PTSD, a subtype of PTSD, or an overarching disorder covering PTSD? From the clinician���s point of view, an ability to comprehend the suffering of patients in an integrated fashion is invaluable for accurate treatment, both psychotherapeutically and biologically.