Plasma levels of endothelin (ET) were determined by radioimmunoassay in 11 healthy volunteers and 34 patients with liver cirrhosis. The results revealed that mean ET plasma level was significantly lower in 34 cirrhotic patients than in normal subjects (40.21 +/- 4.38 ng/L vs 84.55 +/- 7.88 ng/L, P < 0.01). Plasma ET was 32.17 +/- 3.98 ng/L in 23 cirrhosis patients with ascites compared with 57.0 +/- 9.0 ng/L in patients without ascites (P < 0.01). Moreover, it is apparent that plasma levels of ET decreased with the increase of ascites volume, and increased after the disappearance of ascites. But plasma levels of atrial natriuretic peptide (ANP) in cirrhotic patients were markedly higher than those in the controls (830.12 +/- 72.18 ng/L vs 439.45 +/- 50.18 ng/L, P < 0.01). In patients with ascites, ET plasma levels were inversely correlated to ANP. The results suggest that deficiency of circulating ET might be one of the important factors involved in sodium and water retention in cirrhosis.