The present clinical trial assessed the effect of double-dose administration of replication-deficient adenovirus-thymidine kinase and ganciclovir (ADV-TK/GCV) in patients with advanced hepatocellular carcinoma (HCC) who underwent liver transplantation (LT). Eighty-six patients with single tumor diameters >5cm or multiple tumors with diameters >3cm each, regardless of vascular invasion, were examined over a follow-up period of 61 months. All patients underwent orthotopic LT; 43 received LT only, and 43 received LT plus double-dose ADV-TK/GCV gene therapy (LT + ADV-TK/GCV). Recurrence-free survival (RFS) and overall survival (OS) rates, as well as therapeutic safety, were assessed. The RFS and OS rates in LT + ADV-TK/GCV patients at 3 years (55.9% and 60.3%, respectively) were significantly higher than those in the LT-only group (13.5% and 19.3%, respectively; p<0.001). LT + ADV-TK/GCV patients without vascular invasion showed significant improvement in RFS (73.7%) and OS (68.6%). LT + ADV-TK/GCV patients without extrahepatic vascular invasion experienced higher OS versus LT-only patients. Double-dose ADV-TK/GCV gene therapy combined with LT was safe and improved RFS and OS in advanced HCC patients without vascular invasion over the 5-year follow-up period. The potential to select patients with intrahepatic and extrahepatic vascular invasion for LT requires further confirmation.