We measured plasma endothelin-1 (ET-1) concentrations in 20 healthy controls and 63 patients with liver diseases including 9 cases of acute hepatitis (AH), 14 cases of chronic hepatitis (CH), 24 cases of liver cirrhosis (LC), 11 cases of hepatocellular carcinoma with LC (HCC), 3 of primary biliary cirrhosis and 2 of idiopathic portal hypertension. ET-1 levels in AH (5.07 +/- 2.54 pg/ml, mean +/- SD), LC (3.71 +/- 1.17) and HCC (3.08 +/- 0.93) were significantly higher than those in healthy controls (2.18 +/- 0.37). ET-1 levels in AH, LC and HCC were also significantly higher than those in CH (2.05 +/- 0.61). ET-1 levels showed negative correlations with serum albumin levels and Ch-Ease activities, and positive correlations with serum bilirubin levels, AST and ALT activities. However, there was no correlation between plasma ET-1 concentrations and concentrations of serum thrombomodulin which is known to be a marker of injured vascular endothelial cells. In cirrhotic patients, ET-1 levels were significantly influenced by the presence of ascites. The results of the present study suggest that plasma ET-1 concentrations may be a useful clinical indicator for use in the follow-up of patients with chronic liver diseases, e.g., progression from CH to LC, and change in grade of portal hypertension and decompensation in LC.