At present, no effective therapy is available for hepatocellular carcinoma, when local treatments have failed. We reported the results obtained with prolonged, ultra-low-dose (1 MIU/d until progression), subcutaneous interleukin-2 (IL-2) in a series of 18 consecutive patients (14 men and 4 women, median age 66 years, range 49-82 years) with advanced, histologically proven HCC on liver cirrhosis. During a median follow-up time of 19.5 months, two complete responses (11.1%), lasting 35 and 46 months, respectively, and one partial response (5.5%) were recorded (overall response rate: 16.6%; 95% CI: 0-33.8%). Thirteen patients (72.3%; 95% CI: 61.6-82.7) had stable disease lasting at least 4 months; 1 of these patients obtained a complete response on lung metastases. Median time to progression was 15.3 months (95% CI: 10-33). Median overall survival was 24.5 months (95% CI: 12-43). Two patients (11.1%) progressed during therapy. Toxicity was only local (usually pain and pomphus in the site of injection). Low-dose IL-2 can be considered an active and well-tolerated treatment for unresectable hepatocellular carcinoma. Future studies on large numbers of patients are necessary to confirm these results.