Natural disasters often increase morbidity and mortality rates. Taking appropriate measures to maintain environmental health helps to reduce or eliminate the risks of preventable disease and death. Such measures contribute not only to the health of individuals in and near disaster-stricken areas, but they also contribute to decreasing the high costs of providing emergency health services in the aftermath of disaster. This document is divided into several parts. The first section primarily addresses the effects of natural disasters on environmental health conditions and services. In the second section, environmental health measures are described that should be undertaken in each of three time frames: the predisaster, disaster, and postdisaster periods.