The National Disaster Medical System (NDMS) is aimed at medical care needs resulting from catastrophic earthquakes, which may cause thousands of deaths and injuries. Other geophysical events may cause great mortality, but leave few injured survivors. Weather incidents, technological disasters, and common mass casualty incidents cause much less mortality and morbidity. Catastrophic disasters overwhelm the local medical care system. Supplemental care is provided by disaster relief forces; this care should be adapted to prevalent types of injuries. Most care should be provided at the disaster scene through supplemental medical facilities, while some can be provided by evacuating patients to distant hospitals. Medical response teams capable of stabilizing, sorting, and holding victims should staff supplemental medical facilities. The NDMS program includes hospital facilities, evacuation assets, and medical response teams. The structure and capabilities of these elements are determined by the medical care needs of the catastrophic disaster situation.