Plasma levels of PGI2 were measured by radioimmunoassay in 20 consecutively admitted cirrhotic patients with portal hypertension from Aug. 1993 to Aug. 1994. It was found that cirrhotic patients with portal hypertension had much higher portal venous PGI2 levels than controls (528.25 +/- 205.48ng/L vs. 235.73 +/- 49.36ng/L, P < 0.001). Portal venous PGI2 levels in patients with cirrhosis and portal hypertension correlated significantly with portal venous pressure (r = 0.60, P < 0.05). The results indicate that increased portal venous PGI2 levels may have a role in maintenance of established portal hypertensive state in cirrhotic patients with portal hypertension.