In this article, evidence that health sector preparedness improves response performance in disasters was examined. Case fatality and survival data were compared for four earthquakes, in relation to health sector emergency preparedness levels. Vast differences in performance were found. The two California systems, with a high preparedness index, had low case fatality rates (about one death per 100 injuries). Kobe, Japan, with mixed levels of preparedness, had 31 deaths per 100 injuries, and Armenia (low preparedness index) had 167. Public health and health sector preparedness made a significant difference in the ability to respond effectively to meet patient needs in disasters, although it is only one of several factors that determine the health outcome of disaster victims.