Endotoxemia without sepsis was detected with a chromogenic Limulus assay in 36 of 39 (92.3%) cirrhotic patients and was absent in seven healthy volunteers. In 11 patients who underwent elective portasystemic shunt, portal vein endotoxemia was higher than inferior vena caval: p less than 0.05, systemic endotoxin levels did not change, compared to preoperative levels, on the 1st, 2nd, and 3rd postoperative days, attendant to an uneventful recovery. In 21 patients in hepatic encephalopathy after esophagogastric hemorrhage, systemic endotoxemia was higher than in well-compensated cirrhotics: p less than 0.001; it was higher in deep than in light coma: p less than 0.05; it was higher in those who died than in those who survived: p less than 0.001. Endotoxin levels showed a positive correlation with serum bilirubin: r = 0.59, p less than 0.001, and a negative correlation with prothrombin activity: r = -0.59, p less than 0.001. These data show endotoxemia without sepsis is a constant finding in cirrhosis and increasing levels of endotoxemia are associated with hepatic failure, encephalopathy, and death.