AN ENVIRONMENTAL CRISIS, such as a flood, can significantly affect health care delivery and services in a community.Environmental disasters can be particularly devastating to already vulnerable populations such as the homeless and migrants, who, because of social, political, and economic constraints, experience special health care needs. In 1993, after Iowa experienced the worst flood in its history, President Clinton declared the entire state a federal disaster area. Later, the Iowa Department of Public Health received a federal grant to evaluate the health care delivered during the flood and develop a strategic plan to enhance primary health care for the homeless and migrant populations during future environmental disasters. The plan was based on data obtained during and after the flood in three critical areas - communication, health care delivery, and community. These areas were themes that emerged from a series of interviews with representatives from health care agencies and clients themselves. Each theme became the focus of specific, comprehensive recommendations and strategies to meet the daily challenges of the homeless and migrants, as well as to enhance the delivery of primary health care services in the future.