I. Contribution of the reticuloendothelial system to the defence of the organism against endotoxins: phagocytic function, blood clearance and detoxifying function. II. Endotoxin--liver cell interaction. A) The effects of endotoxin on the parenchymatous liver cell; morphofunctional alterations: endotoxicosis as a "set of hepatic metabolic lesions". B) The sensitivity to endotoxin of organisms whose liver has undergone a functional alteration. III. Intrahepatic detoxification of endotoxin--an enzymatic process:--the role of enzymes oxidizing fatty acids;--the role of enzymes containing SH groups; --the role of tryptophane-oxygenase. IV. Conclusions.