Complex, humanitarian emergencies, the result of civil strife and armed conflict affecting large populations at the brink of extinction, represent the most compelling of disaster relief challenges. They require the coordination of the United Nations agencies, the International Committee of the Red Cross, international nongovernmental relief organizations, and military forces. An increasing number of civilian and military health-care providers find themselves involved in the planning, coordination, and direct patient-care aspects of these emergencies, often without proper initiation and understanding of the unique nature of these disasters. This article provides a primer on the concept of complex, humanitarian emergencies and the contributions, characteristics, capabilities, and limitations of each major participant.