Regarding the high prevalence of traumatic experiences in patients with borderline personality disorders (BPD), we review the available literature focussing on the hypothesis that BPD is a subtype of trauma associated disorders. The criteria of BPD, of complex post-traumatic stress disorders (PTSD), and of disorders of extreme stress not otherwise specified (DESNOS) substantially overlap. Research of the long-term course of BPD and PTSD, trauma research, and research of vulnerability in both disorders yielded converging results. Neuropsychological deficits in BPD and PTSD as well as psychoendocrinological and neuroimaging studies in BPD und PTSD also revealed common features. A pathogenetic specificity of individual etiologic factors does not appear to exist, however the assumption of a diathesis-stress model with traumatisation as a necessary but etiologically insufficient condition seems justified. Further research will have to prove BPD as a complex and early-onset post-traumatic stress disorder after multiple and/or chronic (type II) traumatic experiences during childhood and/or youth. Definitive conclusions require further research efforts.