Polycystic liver disease is commonly asymptomatic but may present with hepatomegaly, abdominal distension, and dull abdominal pain. Transudative ascites is a rare manifestation in these patients but may occur when portal hypertension is present resulting from associated hepatic fibrosis or after deroofing procedure of a cyst. Exudative ascites might suggest hepatic venous outflow obstruction. Four cases are described where hepatic venous outflow obstruction occurred in patients with polycystic liver disease. Three patients had orthotopic liver transplantation and one had a mesocaval shunt. Of the two patients that survived orthotopic liver transplantation both have shown considerable improvement in their symptoms. None of the patients had any confirmed procoagulant disorder. The mechanism of hepatic venous outflow obstruction in these patients seems to be mechanical compression of hepatic veins by the cysts and associated formation of thrombi in small hepatic vein tributaries. Patients with severe polycystic kidney/liver disease are at risk of hepatic venous outflow obstruction and the onset of this complication is heralded by tender hepatomegaly and presence of exudative ascites.