Endotoxemia, measured by Limulus amebocyte lysate (LAL) assay, was found to be present in 34 (46%) out of 72 patients with liver cirrhosis and in 7 (22%) out of 32 patients with chronic active hepatitis (CAH). In cirrhotics, no difference in the alteration of liver function tests and renal function was found between the two groups. However, 18 months mortality was higher in the group with endotoxemia in respect to the group without endotoxemia (p less than 0.05). In CAH patients, the Limulus-positive group showed a higher level of serum gamma-globulins, compared to the Limulus-negative group (p less than 0.005). Moreover, CAH patients with a positive LAL test showed marked histological activity and bridging necrosis more frequently than those with a negative test. This suggests that in these patients the appearance of endotoxemia may indicate a more advanced stage of the disease.