1. Endotoxins are very potent and widely spread inflammation-inducing substances. 2. In the course of local infections endotoxins represent one of the main principles of the pathogenicity of gram-negative bacteria by inducing acute nonspecific inflammation. 3. The pharmacological activities of endotoxins consist primarily in generating and liberating the classic mediators of acute nonspecific inflammation. 4. Endotoxins are able to enter into the circulation through their capicity to activate pharmacological mediators. 5. The endotoxic mediators which increase the permeability of the microcirculation of the intestinum enable endotoxins as components of the physiological intestinal flora to enter into the circulation; these induce systemic disease or shock depending on their concentration in the circulation. 6. In the course of chronic inflammation recidivism or recrudescence as trasient acute inflammatory outburst can be caused by local effects of endotoxins. 7. According to some recent observations the inflammation inducing capacity of endotoxins may promote the entry of aerobic bacteria into the blood stream which can result in mixed septicemia.