The term viral hemorrhagic fever refers to a clinical syndrome characterized by acute onset of fever accompanied by nonspecific findings of malaise, prostration, diarrhea,and headache. Patients frequently show signs of increased vascular permeability, and many develop bleeding diatheses. The hemorrhagic fever viruses represent potential agents for biologic warfare because of capability of aerosol transmission, high morbidity,and mortality associated with infection, and ability to replicate in cell culture in high concentrations. Herein we discuss the Filoviridae, the agents of Ebola and Marburg hemorrhagic fevers.