Objective. Violence is widespread in Australian emergency departments (ED) and most prevalent at triage. The aim of the present study was to identify the causes and common acts of violence in the ED perceived by three distinct groups of nurses.Methods. The Delphi technique is a method for consensus-building. In the present study a three-phase Delphi technique was used to identify and compare what nurse unit managers, triage and non-triage nurses believe is the prevalence and nature of violence and aggression in the ED.Results. Long waiting times, drugs and alcohol all contributed to ED violence. Triage nurses also indicated that ED staff, including security staff and the triage nurses themselves, can contribute to violence. Improved communication at triage and support from management to follow up episodes of violence were suggested as strategies to reduce violence in the ED Conclusion. There is no single solution for the management of ED violence. Needs and strategies vary because people in the waiting room have differing needs to those inside the ED. Participants agreed that the introduction and enforcement of a zero tolerance policy, including support from managers to follow up reports of violence, would reduce violence and improve safety for staff. Education of the public regarding ED processes, and the ED staff in relation to patient needs, may contribute to reducing ED violence.What is known about the topic? Violence is prevalent in Australian healthcare, and particularly in emergency departments (ED). Several organisations and government bodies have made recommendations aimed at reducing the prevalence of violence in healthcare but, to date, these have not been implemented consistently, and violence continues. What does this paper add? This study examined ED violence from the perspective of triage nurses, nurse unit managers and non-triage nurses, and revealed that violence is experienced differently by emergency nurses, depending on their area of work. Triage nurses have identified that they themselves contribute to violence in the ED by their style of communication.Nurse unit managers and non-triage nurses perceive that violence is the result of drugs and alcohol, as well as long waiting times. What are the implications for practitioners? Strategies to reduce violence must address the needs of patients and staff both within the ED and in the waiting room. Such strategies should be multifaceted and include education of ED consumers and staff, as well as support from management to respond to reports of violence.