Five patients with hepatocellular carcinoma were subjected to immunotherapy: three patients were treated by adoptive immunotherapy with lymphokine-activated killer (LAK) cells and recombinant interleukin-2 (rIL-2), and two patients by systemic administration of rIL-2 alone. In one patient with diffuse-type hepatocellular carcinoma and portal vein thrombosis who was treated by infusion of LAK cells (a total number of 1.5x1010 cells/13 doses) and continuous rIL-2 administration (a total dose of 1.25x108 units) via a percultaneously placed hepatic arterial catheter, the size of the tumor reduced dramatically and the portal vein thrombosis retracted. In two patients who had LAK cells infused (totals of 6.6x109 cells/4 doses and 3.1x109 cells/2 doses, respectively) during hepatic angiogram followed by systemic administration of rIL-2 twice a day, no clinical improvement was noticed. In two patients who received rIL-2 alone systemically (total doses of 8.9x107 and 5.5x107 units, respectively), neither clinical improvement nor severe side effects were observed. The results suggest that adoptive immunotherapy combined with continuous local administration of rIL-2 via a percutaneously placed hepatic arterial catheter may be an effective therapy without apparent side effects for patients with hepatocellular carcinoma who cannot be treated by conventional cancer therapy.