Although disasters have exacted a heavy toll of death and suffering, the future seems more frightening. Good disaster management must link data collection and analysis to the decision-making process. The overall objectives of disaster management from the viewpoint of public health are: 1) needs assessments; 2) matching available resources with defined needs; 3) prevention of further adverse health effects; 4) implementation of disease-control strategies; 5) evaluation of the effectiveness of the application of these strategies; and 6) improvement in contingency planning for future disasters. The effects of sudden-onset, natural disasters on humans are quantifiable. Knowledge of the epidemiology of deaths, injuries, and illnesses is essential to determine effective responses; provide public education; establish priorities, planning, and training. In addition, the temporal patterns for the medical care required must be established so that the needs in future disasters can be anticipated. This article discusses: 1) the nature of disasters due to sudden-onset, natural events; 2) the medical and health needs associated with such events and disasters; 3) practical issues of disaster responses; and 4) the advance organization and management of disasters. The discussion also includes: 1) discussions of past problems in disaster management including non-congruence between available supplies and the actual needs of the affected population; 2) information management; 3) needs assessments; 4) public health surveillance; and 5) linking information with decision-making. This discussion is followed by an analysis of what currently is known about the health-care needs during some specific types of sudden-onset, natural disasters: 1) floods; 2) tropical cyclones; 3) tornadoes; 4) volcanic eruptions; and 5) earthquakes. The article concludes with descriptions of some specific public-health problems associated with disasters including epidemics and disposition of corpses. All natural disasters are unique in that the regions affected have different social, economic, and health backgrounds. But, many similarities exist, and knowledge about these can ensure that the health and emergency medical relief and limited resources are well-managed.