Endotoxins of gram-negative bacteria and of intestinal origin, insufficiently cleared by the hepatic reticulo-endothelial system are of an increasing interest within the pathogenesis of liver diseases. With purpose to obtain data concerning incidence and course of endotoxaemia in patients with liver cirrhosis an unselected group of these patients, sequentially admitted, was investigated by means of the Limulus-gelation test, regarded as most sensitive to endotoxins. At the admittance, 65% of the patients had endotoxaemia, further 14% developed endotoxaemia later. In total 79% of the patients investigated had endotoxaemia.---Bleeding from oesophageal varices was associated with endotoxaemia in 78%, functional renal impairment in 75%, consumption coagulopathy in 81%, encephalopathy in 77% and a pyrogen reaction in 82% of the patients. Regarding the Limulus assay, the dilution technique was more sensitive in detection of free endotoxaemia as opposed to the chloroform extract. It is concluded from the results that endotoxaemia in patients with liver cirrhosis is frequent and has to be viewed as relevant within the pathogeneses of chronic liver diseases.