Epidemics caused by microorganisms have deeply affected societies and political mechanisms throughout history, causing serious consequences. Because of the epidemic diseases, economies have collapsed, the population has decreased, the social structure has been damaged, and even some states and empires have been destroyed. Even if the causes of deseases were unknown in those years, based on the observation of the results, people and emperors tried to develop methods suitable for their interests, used biological substances for the purpose of war and attack. Many methods have been used in history, from the Carthaginian general Hannibal throwing poisonous snakes in pots on the ships of Pergamon during the war with the King of Pergamon (Eumenes II) to the Japanese attacks with plague fleas in the second World war. Although the use of biological substances in wars between states is prohibited by the “Biological Weapons Convention", which entered into force on March 26, 1975, some states have continued to produce these weapons under the guise of defense and continue to do so.  Moreover, biological agents have attracted the attention of not only states, but also terrorist organizations such as “Aum Shirinkyo” and “Rajneesh cult”, and other malicious individuals such as Ivins or Pandey, and have started to be used. For today, the interest of states, terrorist organizations and malicious individuals in biological agents has not decreased. It can even be said that it continues to increase. it is estimated that around 20 countries continue to be studied under various research and projects and in high-security laboratories. This type of research continues to increase in laboratories called Biological level 4 (BSL4), which are designed to work with extremely dangerous microorganisms and biological substances. International independent audits cannot be carried out in these laboratories, so the studies are conducted far from open and transparent. Lack of supervision causes these laboratories to become a “Pandora's box” for the scientific world and causes doubts.  Biological agents, whether by making natural epidemics or in the form of their abuse, will continue to be a greater threat to humanity than the nuclear danger. In this study, it was reviewed what great disasters biological agents have caused for humanity throughout history and it was aimed to raise awareness about the dangers of today.