The authors present 225 patients with various forms of portal system venous thrombosis (PSVT), of various origin and etiology. The largest group (120 patients) were the young people suffering from portal hypertension due to pre-hepatic venous obstruction of uncertain etiology, lasting since childhood. The next group consisted of 75 patients with liver cirrhosis coexisting with PSVT. In other cases PSVT was diagnosed as coincident with: Budd-Chiari Syndrome (8 cases), liver tumors (9 cases), chronic pancreatitis (3 cases) and polycythaemia (2 cases). In 3 cases PSCT developed postoperatively and in 5 cases after oral contraceptives. Diagnosis of coexisting PSVT deteriorates the prognosis in liver cirrhosis. The overall mortality was 16%. The course of the disease depends on extensiveness and dynamism of thrombosis, but consequently leads to the development of portal hypertension. The most effective diagnostic procedures are: CT and USG with Doppler flowmetry. Bleeding esophageal varices require either sclerotherapy or surgical treatment--decompressive shunts or "non-shunt" procedures. In the cases of recent thrombosis, without bleeding varices, thrombolytic therapy appears to be effective.