Experimental studies have showed that hepatocellular carcinoma (HCC) cells are susceptible to cytolysis of interleukin (IL)-2-activated lymphocytes. Moreover, our previous studies demonstrated that the pineal neurohormone melatonin (MLT) may enhance IL-2 efficacy. On this basis, a study was started with low-dose IL-2 (3 million U/day subcutaneously for 6 days/week for 4 weeks) plus MLT (50 mg/day orally every day given in the evening) as a first-line therapy of unresectable HCC. The study included 14 patients. Objective tumour regressions were obtained in 5/14 (36%) patients (one complete response, four partial responses), with a median duration of 7+ months. 6 patients had stable disease, while the other 3 progressed. Toxicity was low in all cases. This study shows that the neuroimmunotherapy with low-dose IL-2 plus MLT is a new well-tolerated and effective therapy of advanced HCC.