We performed 70 proceudres of transarterial chemoembolization (TAE) through extrahepatic collateral vessels (n=27) or parasitic feeders (n=18) in 45 hepatocellular carcinoma patients. The collaterals developed after interruption of the hapatic artery due to repeated TAE(n=17), surgical ligation(n=7) and primary celiac occlusion (n=3). Radiologic findings suggesting the existence of parasitic or collateral supply for hepatocellular carcinoma were 1) a focal defect of Lipiodol retention on CT or plain film after TAE via the hepatic artery, 2) dilated and tortuous vessels around the mass on angiography, 3) persistent elevation of the level of serum alpha fetoprotein or continuous clinical symptoms in spite of sufficient devascularization of the tumor via the hepatic artery, and 4) radiological findings of direct invasion into adjacent organ. The sites of the catheter placement were the inferior phrenic artery (n=19), omental branches (n=16), periportal collaterals (n=6), pancreaticodenal arcade (n=3), gastroduodenal artery (n=3), internal mammary artery (n=2), intercostal artery (n=2), lateral thoracic artery (n=1), bronchial artery(n=1), and colic branches(n=1). Masses feeded by the inferior phrenic and chest wall collaterals were usually located at the dome area of the liver, and the omental and gastroduodenal collaterals developed in the masses located at the inferior tip of the liver. After TAE via collateral vessels, 37 patients underwent follow-up study. In 18 cases(48%), the tumor favorably responded to TAE. Specific complications of collateral TAE were epigastric soreness (n=10), severe shoulder pain (n=4), and embolization of the spinal artery during embolization through the intercostal artey (n=1). In conclusion, various extrahepatic collaterals are important alternative or additional routes for effective chemoembolization in patients with advanced hepatoma, and early recognition of the parasitic supply and the effort to perform TAE via collaterals is very important for effective management of the patients with the hepatoma.