The prevention of tumor recurrence after curative treatment of hepatocellular carcinoma (HCC) is unresolved. Postoperative intraarterial injection of (131)I-labeled lipiodol has been proposed as adjuvant treatment. The aim of this prospective randomized trial was to evaluate if a single dose of postoperative adjuvant intraarterial (131)I-lipiodol (vs. unlabeled lipiodol) could reduce the rate of intrahepatic recurrence at 2 y. METHODS Patients who underwent curative treatment for HCC and recovered within 6 wk were randomly assigned to receive a single 2,200-MBq (131)I-lipiodol dose or a single unlabeled lipiodol dose on a 1:1 basis. Recurrence-free and overall survival rates were analyzed. RESULTS Between June 2005 and February 2009, we included 58 patients (median age of 63 y [range, 23-85 y]): 29 received intraarterial (131)I-lipiodol and 29 received lipiodol adjuvant treatment. At 2 y after treatment, the rate of patients with intrahepatic recurrence was 28% in the (131)I-lipiodol group and 56% in the lipiodol group (P = 0.0449). The Kaplan-Meier analysis confirmed this result, with a 2-y recurrence-free survival in the (131)I-lipiodol and lipiodol groups of 73% and 45%, respectively (P = 0.0259). The 5-y recurrence-free survival rates in the (131)I-lipiodol and lipiodol groups were 40% and 0%, respectively (P = 0.0184). The overall and specific survivals were not significantly different between groups (P = 0.9378 and P = 0.1339, respectively). (131)I-lipiodol had no severe toxic effects. CONCLUSIONS After curative treatment of patients with HCC, one 2,200-MBq dose of intraarterial (131)I-lipiodol significantly decreased the rate of intrahepatic recurrence but failed to improve overall or specific survival.