We report here complications of percutaneous transhepatic catheterization of the portal venous system in 170 Japanese patients with portal hypertension. All patients underwent percutaneous transhepatic portography and percutaneous transhepatic obliteration of oesophagogastric varices was also performed in 29 patients. After retraction of the catheter, the puncture canal was plugged with gelatin sponge in 150 subjects and with one steel coil in 20 others. The overall complication rate was 16.5%. Intraperitoneal bleeding occurred in 10.6% of patients and 2.9% required blood transfusion. In these patients with intraperitoneal bleeding, the gelatin sponge was used for plugging after retraction of the catheter, while in the 20 patients with a steel coil plug, haemoperitoneum never occurred. Right pleural effusion was recognized in 3.5% of patients, intraperitoneal bile leakage in 1.8% and deterioration of liver function due to arteriovenous fistula in 0.6%. By univariate and multivariate analyses, female gender was the only risk factor for intraperitoneal bleeding among 150 patients investigated by percutaneous transhepatic catheterization of the portal venous system with gelatin sponge plugging. Intraperitoneal bleeding is the most important complication in patients with portal hypertension; it is difficult to predict intraperitoneal bleeding before retraction of the catheter in patients for whom gelatin sponge is used. Thus, for patients undergoing percutaneous transhepatic catheterization of the portal venous system, close follow up is recommended.