Tumor necrosis factor alpha (TNF alpha) and interleukins (IL) are the principal cytokines involved in the clinical and biological manifestations of septic shock. Their secretion are triggered mainly by endotoxin, but products of Gram positive cocci as well as of virus or of parasites are equally effective. Cytokines represent a normal protective defense against infection, but an excessive production have toxic effects. In experimental models of endotoxinemia, TNF alpha is the first cytokine produced, then IL-1 and IL-6. Other inflammatory mediators are secreted later. Thus it seems logical to try to modulate cytokine production or actions. However, several questions remains since experimental data are sometimes not applicable too human diseases, cytokines are organised in a network with several interaction. It is too early to propose routine anti-cytokines drugs in septic shock.