Mass casualty events provide dramatic challenges for trauma centers and trauma systems. We analyzed the management of victims and assessed the response of the UCLA Healthcare System to the Santa Monica multicasualty event of July 16, 2003, when an elderly man drove his car through a crowded outdoor market and injured 73 people, 10 of whom died (eight at the scene). Of the victims, 26 were treated at UCLA (n = 15) and Santa Monica (n = 11) Medical Centers. Fourteen patients (54%) were female; average age was 41.9 years (range 7 months to 88 years). Fifteen patients were treated in the ER only, and 11 patients required admission. Of the latter, 10 (91%) had multisystem injuries, most commonly musculoskeletal, which occurred in nine patients (82%). Seven patients required immediate operations (orthopedic in six and a pericardial window in one). Three patients required delayed operations (orthopedic and plastic surgery). Most surgical and medical specialties were needed in consultation. Average LOH was 11.8 (range 2-23) days. Mean ISS was 21.2 (range 1-75). There were six complications (three early and three late) and one death from head injury. Seven patients (64%) required rehabilitation. We conclude that mass casualty victims have multisystem injuries of variable severity, which underscores the importance of trauma centers and trauma systems. The large trauma scene and particular need for orthopedic services were notable features of this event.