Violence towards healthcare staff is increasingly prevalent in today's NHS. The aim of this thesis was twofold: to establish the current state of research into this problem; and to contribute to the theoretical understanding of one of the common outcomes of this phenomenon: posttraumatic stress disorder. The literature review assessed research relating to the incidence, prevalence and effects of workplace violence (WPV), focussing on healthcare settings. Studies indicate a range of effects on victims including physical injury, behaviour changes and psychological symptoms, although methodological problems exist with this research. Also lacking is an over-arching psychological framework to account for the full effects of WPV. Models accounting for PTSD are described and drawn upon to outline psychological methods necessary to develop such a framework. In the current study, psychological response variables were investigated for their involvement in the development of persistent symptoms of PTSD in 99 NHS staff exposed to violence at work. Factors associated with PTSD symptoms at four months post-trauma included: disorganised memory, data-driven processing, state dissociation, self referent processing, appraisal of PTSD symptoms, trait dissociation and avoidant behaviour. All these factors accounted for significant variance in PTSD symptoms after controlling for pre-trauma and stressor severity factors. A risk index consisting of `educational qualification', `trait dissociation' and 'avoidant behaviour', measured two months post-trauma, discriminated individuals with persistent symptoms at four months post-trauma from those without. This enabled better than chance predictions to be made. Further validation is required. Clinical implications are discussed.