UN agencies and international and nongovernmental organizations are increasingly called upon to respond to large-scale emergencies to prevent and manage serious threats to the survival and health of the affected populations. Medicines and medical devices have been supplied by relief agencies for decades. In the 1980s, the World Health Organization (WHO) facilitated a process to encourage the standardization of medicines and medical devices needed in emergencies to allow efficient and effective responses to the need for medicines and medical devices. This initial work led to the supply of standard, pre-packed kits that could be kept in readiness to meet priority health needs in emergencies. The concept of the emergency health kit has been adopted by many organizations and national authorities as a reliable, standardized, affordable and quickly available source of the essential medicines and medical devices (renewable and equipment) urgently needed in a disaster situation. Its content is based on the health needs of 10,000 people for a period of three months. The Interagency Emergency Health Kit, now in its fourth edition, explains how to use standardized packages of essential medicines, supplies and equipment in such circumstances. The fourth edition improves the kit content and takes into account the need for mental health care in emergency settings and the special needs of children. This document provides background information on the composition and use of the emergency health kit. Chapter 1 describes supply needs in emergency situations and is intended as a general introduction for health administrators and field officers. Chapter 2 explains the selection of medicines and medical devices--renewable and equipment--that are included in the kit, and also provides more technical details intended for prescribers. Chapter 3 describes the composition of the kit, which consists of basic and supplementary units. The annexes provide references to treatment guidelines, sample forms, a health card, guidelines for suppliers, other kits for emergency situations, a standard procedure for importation of controlled medicines, and useful addresses. A feedback form is also included to report on experiences when using the emergency health kit, and to encourage comments and recommendations on the contents of the kit from distributors and users for consideration when updating the contents. This is an interagency document published by the WHO Department of Medicines and Pharmaceutical Policies on behalf of the organizations listed.