The viruses that cause hemorrhagic fever belong to four virus families: the Arenaviridae, Bunyaviridae, Filoviridae and Flaviviridae. These viruses are candidates for biological warfare agents because they are stable when aerosolized and cause severe debilitating disease. Research and development regarding the use of these viruses as warfare agents has been performed in the former Soviet Union and other countries. The introduction of these agents into non endemic countries poses a major public health threat to that country. Israel is not endemic for these agents, and therefore, local infection can occur from a traveller (human or animal) from an endemic country or due to intentional dissemination. Major clinical manifestations of hemorrhagic fevers are that of fever, rash, malaise and hemorrhagic signs. Due to the similarity between syndromes, any person with a history of persistent fever and any sign of hemorrhage should be considered as having viral hemorrhagic fever, and appropriate care instituted. Definitive diagnosis requires laboratory testing and is important to identify a possible biological warfare attack and to prepare for appropriate defense. This paper reviews the viruses that cause hemorrhagic fever, and their role as possible warfare agents.