Disasters are not merely very large accidents. They imply complex public health problems that must be resolved under difficult circumstances: society's normal coping mechanisms are disrupted; the high visibility and critical coverage provided by the mass media make the situation politically sensitive; logistic nightmares abound; the multi-agency response from outside the affected area is often poorly coordinated. In short, decision-making in a climate of uncertainty is the norm. Information management, not the medical management of patients, is often the main challenge facing health managers and volunteers in the initial or relief stage of a disaster.