This guidance document has been produced by the World Health Organization (WHO) to assist blood services in the development of national plans to respond to any disaster, major incident or emergency that threatens sufficiency or safety of the blood supply. Such situations can be caused by natural forces, by factors influenced by humans or directly caused by humans. This document is intended to guide the national blood service through the process of planning how to respond in a timely, controlled and appropriate way to emergencies. In the preparation of the document, WHO has tried to include the elements that blood services or providers might need to consider, providing some background on the reasons for their inclusion and guidance on different response options that may be available. The consequences of an emergency may include interruption of blood supply due to a shortage of blood donors, or to a disrupted supply of critical materials and equipment used in blood collection, component preparation and laboratory testing, resulting in reduced availability of blood and blood components. Although the demand for transfusion may decrease in some situations, transfusions continue to be necessary for clinical emergencies and for those patients reliant on long-term transfusion support. In contrast, some emergencies, for instance those resulting in multiple casualties, could lead to a rapid surge in demand for blood over a short time. The challenge is to maintain essential transfusion services as well as responding to the emergency. Preparedness, including business continuity planning, is essential for blood services to mitigate the impact of emergencies. Preparation should be underpinned by locally sensitive risk assessment using relevant data at the local or country level. However, it is not possible to predict the nature of every situation that could impact on the blood supply, and it is therefore expected that blood services will review the elements in this document as well as assessing their own situation, needs, capabilities and resources, along with any additional relevant country-specific factors, in the development of their own response plans. Planning should consider the concurrence and combinations of events and the response should be proportionate and coordinated with others. The aim is to maintain critical services and prepare for recovery. Staff training and support is key to resilience. It is acknowledged that as well as affecting the sufficiency and safety of blood supply, major incidents in countries undertaking transplantation may threaten the safety and sufficiency of the supply of other products of human origin, such as cells, tissues and organs. Increasingly, blood services are taking overall national responsibility for transplantation in their capacity as the organization responsible for the collection, processing, storage and supply of cells, tissues and organs. This approach is both sensible and appropriate, as the overall donor selection and screening processes are the same or very similar. This guidance document can therefore also be used to assist those bodies responsible for the provision of cells, tissues and organs to prepare for emergencies. Resilience to disasters and emergencies requires a commitment to the blood supply and transfusion system as an integral part of the health care system.