In large disasters, such as earthquakes and hurricanes, rapid, adequate, and documented medical care and distribution of patients are essential. After a major (magnitude 6.7 Richter scale) earthquake occurred in Southern California, nine disaster medical assistance teams and two Veterans Administration (VA) buses with VA personnel responded to staff four medical stations, 19 disaster-assistance centers, and two mobile vans. All were under the supervision of the medical support unit (MSU) and its supervising officer. This article describes the patient-data collection system used. All facilities used the same patient-encounter forms, log sheets, and medical treatment forms. Copies of these records accompanied the patients during every transfer. Centers for Disease Control and Prevention data classifications were used routinely. The MSU collected these forms twice each day so that all facilities had access to updated patient flow information. Through the use of these methods, more than 11,000 victims were treated, transferred, and their cases tracked during a 12-day period. Use of this system by all federal responders to a major disaster area led to organized care for a large number of victims. Factors enhancing this care were the simplicity of the forms, the use of the forms by all federal responders, a central data collection point, and accessibility of the data at a known site available to all agencies every 12 hours.