Arteriovenous shunting has been reported in hepatocellular carcinoma (HCC) and is a recognized contraindication to treatment by transcatheter arterial chemoembolization. This study aims to determine the prevalence of arteriovenous shunting in patients presenting with HCC and the development of shunts in those with inoperable HCC being treated with repeated chemoembolization. In a group of 292 Chinese patients (251 men, 41 women; mean age 54.7 years) presenting with HCC, hepatic angiograms demonstrated arteriovenous shunting in 91 cases (31.2%); shunting into the portal vein was observed in 84 (28.8%) and shunting into the hepatic vein in seven (2.4%). The hepatic angiograms of a separate group of 171 Chinese patients (144 men, 27 women: mean age 55.4 years) undergoing chemoembolization for inoperable HCC were analysed. Arteriovenous shunting developed during treatment in 20 patients (11.7%). Of these 20 patients, one had shunting into the hepatic vein while 19 (11.1%) had arterioportal shunting. Arteriovenous shunting occurred through the tumour or portal vein tumour thrombus in 13 patients, and occurred at sites remote from the tumour in the other seven patients. Shunting disappeared on repeat angiograms in three patients. Various postulated mechanisms responsible for arteriovenous shunting in HCC are reviewed. The recognition of development of arteriovenous shunting during chemoembolization of HCC is important as it has a direct bearing on patient management and prognosis.