Violence at work (VAW) is a frequent precursor to mental ill health, and to a lesser degree physical injury, among those exposed to this occupational hazard. In this paper an overview is provided of the nature and prevalence of such violence, of the risk factors involved, and of the impact upon victims. The paper examines the definition of VAW which includes both physical and psychological violence. Attention is given to the influential involvement of the UN affiliated International Labour Organisation in setting benchmarks for defining, preventing and responding to VAW. Evidence about the incidence and severity of VAW on a global basis is examined. It is noted that the reliability of information about VAW is quite variable, especially in non-industrialised countries. The available evidence indicates that psychological aggression is widespread across all sectors of employment and physical violence, although far less common, remains a significant problem. Risks of becoming a victim of VAW vary according to numbers of factors including job category, the nature of the work being performed, gender, age and experience. The paper also focuses on research regarding the effects upon persons experiencing or witnessing VAW. This research indicates that the health related consequences of psychological violence can be as severe as those from physical violence. The paper concludes that VAW is a major occupational health and safety hazard in all nations, regardless of their state of development. A reduction or elimination of this violence, and the health problems it creates, requires concerted and integrated strategies, together with rigorous evaluation of preventive measures.