[en] During sepsis, the systemic inflammatory response is characterized by the release of numerous mediators supporting and dispersing inflammation. In Gram negative sepsis, the endotoxins play a starting role, while in other sepsis, the triggering mediators or mechanisms are unknown but lead to a similar inflammatory reaction. Coagulation and complement cascades are activated, with the release of chemoattractive substances, mediators and proteases and the activation of phagocytic cells. Macrophages/monocytes and polymorphonuclear leucocytes produce then active oxygen species and cytokines; they degranulate (releasing active enzymes such as myeloperoxidase), they express an increasing number of membrane receptors able to interact with endothelial cells and release a supplementary lot of inflammatory mediators (prostanoids, platelet activating factor, leukotrienes ... ). Platelets, also activated, produce the same mediators (TXA2, PAF ...) or specific ones such as serotonine, platelet factor 4, growth factors. Last, but not least, the endothelial cells are stimulated, directly (by endotoxins) or undirectly (by cytokines, C5a, PAF ...). These cells play then a main role by their own phagocytic activity, by alteration of their antithrombotic and fibrinolytic potential, by their secretion of inflammatory mediators and by an increased expression of receptors of adhesivity for the activated phagocytes or platelets, what leads to endothelium injury with membrane permeability alterations. These cascades of activation, these extensions of the inflammatory reaction by the mediators and by the phagocytes and platelets can explain the frequency of multiple organ failure during sepsis as well as the difficulty of an adequate pharmacological therapy.