The terrorist attacks on and after September 11, 2001 have drawn attention to the fact that besides the traditional warfare, microorganism-based weapons are playing greater and greater role in military activities, especially in terror attacks. The ongoing war activities worldwide and the continuing international conflicts suggest that despite the international treaties, sooner or later germ warfare must be considered. The relatively easy preparation, storage and application of biologic weapons, despite the strictly regulated access, hold out major advantages when compared to traditional warfare, especially for terrorist activities. Germ warfare, divided into three different categories by the Center for Disease Control and Prevention USA, are based on use of bacteria, toxins and viruses. Besides the causative agents of the traditionally fearful contagious diseases (plague, smallpox, anthrax) other biologic agents (toxin of C. botulinum, hemorrhagic fever viruses) also play an important role in biologic warfare. Cognition of biologic weapons is very important because the infections originate from causative agents existing in the natural environment, but are generated artificially. These infections, whether air or food born, may generate numerous infections. Since the initial clinical features are usually not characteristic for the disease, it is crucial to be aware of the circumstances and clinical symptoms indicating biologic attack when produced en masse. When bio attack is recognized in time, suitable countermeasures may effectively reduce the severeness and expansion of the resulting infection.