The gradient between wedged and free hepatic venous pressures were measured in 10 unselected adult patients suffering from fulminant viral hepatitis. The gradient was increased in all the studied patients, ranging from 0.9 to 2.1 kPa; this finding indicates that portal hypertension was present in all these cases. Ascites was present in all the five patients having a gradient about 1.5 kPa and affected only two of the five patients having a gradient below 1.5 kPa; this observation suggests that portal hypertension plays a role in the mechanism of ascites in fulminant viral hepatitis. Portal hypertension in fulminant viral hepatitis is likely to be the consequence of an intrahepatic block due to massive necrosis of the liver cells.