In developing this third revision of version 4.0 of the Field Operations Guide for Disaster Assessment and Response, the Office of U.S. Foreign Disaster Assistance (OFDA) of the United States Agency of International Development (USAID) has drawn on the expertise of numerous state, national, and international agencies and organizations. Selected sources of information include the United Nations High Commissioner for Refugees’ Handbook for Emergencies, the United Nations Office for the Coordination of Humanitarian Affairs’ United Nations Disaster Assessment and Coordination Field Handbook, and the U.S. Public Health Service’s Handbook of Environmental Health, among others. The Field Operations Guide for Disaster Assessment and Response has been created as a reference tool for individuals sent to disaster sites to undertake initial assessments or to participate as members of a Disaster Assistance Response Team (DART). It contains information on general responsibilities for disaster responders, formats and reference material for assessing and reporting on populations at risk, DART position descriptions and duty checklists, descriptions of OFDA stockpile commodities, information for working with military in the field, and much more. Its myriad resources, extensive information, and handy compact format make this field guide a necessary companion for those participating in a variety of disaster assessment and response field operations.